Knowledge driven composite design optimization process and system therefor

ABSTRACT

A knowledge driven composite design optimization process for designing a laminate part includes steps for generating a globally optimized 3-D ply definition for a laminate part, and modifying the 3-D ply definition to include features of the laminate part, where the generating and modifying steps are parametrically linked to one another and are performed in the recited order. Preferably, the generating step includes substeps for determining connectivity between a plurality of regions defining the laminate part, subsequently generating ramp features detailing interconnection of the regions defining the laminate part, and displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user. A knowledge driven composite design optimization system and associated computer memory for operating a general purpose computer as a knowledge driven composite design optimization system are also described.

BACKGROUND OF THE INVENTION

The present invention relates generally to a composite materials designprocess. More specifically, the present invention relates to a knowledgedriven composite design optimization process and corresponding system. Acomputer program adapted to facilitate implementation of the knowledgedriven composite design optimization process is also disclosed.

The use of composites in airframe construction is becoming anincreasingly complex process. Composite structures are generallydesigned at the local laminate level using wireframes or solids inComputer Aided Design (CAD) systems such as the UNIGRAPHICS (TM) CADsystem. Analysis is performed using a separate analytical model(s),e.g., a finite element based model, which initially assumes laminatefamilies which define a percentage composition (number) of each plyorientation and which is generally coordinated with design geometrythrough imported master datums and a design surface. A typical designprocess is illustrated in the functional flowchart of FIG. 1. From theflowchart, it will be appreciated that the current design process hasnot been optimized. For example, finite element analysis (FEA) isconducted before the step of editing the ply lay-up formanufacturability, which virtually guarantees that the FEA step willhave to be repeated and, in many cases, repeated several times.Moreover, it will be appreciated that changes in, for example, thewireframe model will require updates to, or recreation of, the finiteelement model and vice versa.

Furthermore, many design considerations are not routinely addressedduring the composite design process. For example, often in theanalytical model, the order in which each oriented ply is found withinthe total number of plies is not considered. Typically, the analyst doesnot restrict the thickness map to "buildable" thicknesses of thematerial selected or specify families which produce "fabricationfriendly" designs. These modifications are typically integrated by thedesigner in their geometry model. However, since the above-mentionedmodifications occur after the bulk of the analysis has been completed,there are often surprises, e.g., higher than expected component weight,at a point well into the design process. In addition, even when theanalyst does define local stacking sequences, the analyst accomplishesthis by performing optimizations which result in local laminatedefinitions which do not integrate well with one another.

It will also be noted that documentation for manufacturing is currentlyprovided in two key ways:

(1) as a design surface with cured ply boundaries projected to a plane;and

(2) through manually created section cuts and laminate tables thatcontain text entities for each ply identifying orientation, material andnumber of each ply.

Since the textual data must be created manually, text data havingmissing information is frequently released to other manufacturingdepartments. When design changes occur, these errors and omissions arecompounded because the text data is often only partially updated aftereach design change.

The inner moldline, which is often a tooled surface and always astructural mating surface, is defined by conceptually joining theresultant section cuts of the engineering. i.e., CAD, definition.Manufacturing personnel then flatten the ply geometry to create uncuredply boundaries that are cut for fabrication. Translation errors due toselection of the incorrect normal orientation during this step are acommon occurrence when working with complex geometry, primarily becausestandards do not address this level of detail. Moreover, while thethickness of the composite material used to create the laminate is18-25% thicker than cured material, this fact is normally not reflectedin any of the traditional models. It should be mentioned that the oneexception to this general statement is found in the unique files whichare created by manufacturing for laser projection that use a "debulked"ply thickness to develop a three dimensional (3-D) plies representationof the part in the lay-up step of fabrication. The variability of thetranslation process is high, since design intent is not always clearbecause all ply boundaries are represented on one 3-D plane rather thanin true 3-D space. An example of the type of defect created with nogeometrical definition at the ply level in 3-D space is describedimmediately below.

The lack of geometrical accountability for ply overlaps leads to locallyundersized areas in tools. This in turn results in increased localpressure on the component during the cure at ply overlap or spliceareas. This may contribute to internal laminate defects in the form ofporosity or resin poor areas in a structure if enough of these detailsoccur through the thickness in an area. In addition, lack of geometricalaccountability can lead to local distortion of the fiber architectureand can result in increased interlaminar shear stress, each of whichadversely affects structural performance. These cause and effectrelationships are viewed as too complex for the current conventionalcomposite process to track and control during design and fabrication. Itwill be appreciated from the references, discussed briefly below, that agreat deal of attention is paid to these effects at the micromechanicslevel in literature and in the typical fabrication shop for specificstructures, yet no standard process allows easy incorporation of theseconsiderations into composite design practices. The current approach tounderstanding these local effects is to build and then cutup compositeparts, i.e., to perform destructive testing of the articles. It will beappreciated that this is an expensive and time-consuming approach tounderstanding a geometrical problem.

In addition, manufacturing constraints such as material widthrestrictions are not incorporated or reflected in the design data. Suchdesign constraints are often considered only as a refinement (iteration)within the manufacturing definition cycle, i.e., when editing plydefinition to ensure manufacturability. It will be noted that thisresults in additional ply splices which may not be accounted for in thedesign. While this often leads to structural degradation, thesemanufacturing constraints may not be reviewed during the design steps incurrent practice. Thus, the analytical community is forced to adoptconservative analysis approaches to avoid the risk created byuncertainties arising from manufacturing constraints. The most commonimpacts of this approach are greater structural weight, more stringentfabrication requirements, and, of course, higher costs. The lack ofunderstanding of the structural design impacts on fabrication also leadsto inconsistent disposition of discrepant fabrication events, since a"preferred" or "best" practice has never been identified. The impactsare considered part of the variability that leads to the reducedmaterial allowables used for composite analysis.

It should also be mentioned that design changes often require updates tomanufacturing data. Manufacturing recreates the textual data at leasttwice to produce data forms that meet the needs of the manufacturingdatabase. The composite database becomes the source for all in-processinspections and fabrication. Final parts are inspected to design data asprepared by manufacturing personnel in their templates and database.Database coordination for design changes is a challenging, not tomention a continuous, process.

Moreover, the only software tool that attempts to integrate thedefinition and analysis of composites is the Northrop Grumman's,formerly Vought Aircraft Company's, Computerized Composite DevelopmentProject (CCDP) program. The CCDP program is limited in that it does notcreate a 3-D product definition, is hard coded in FORTRAN to run on aVAX computer or computer cluster, and includes no adaptive knowledge orobjects that can assist the designer in tracking sensitivities of designchanges. Moreover, the CCDP program is not focused on visualization,parametric definition, or 3-D design capabilities. While the CCDPprogram does a relatively good job of integrating manufacturing dataneeds into the program and outputting documentation, the CCDP programsimply cannot provide any documentation in the form of blueprints orother visual aids. In addition, the CCDP program is unable to duplicatethe optimum laminate selection of an analyst without manualintervention.

What is needed is a process for designing composites which establishes aglobal, manufacturable laminate definition at the ply level.Additionally, what is needed is a knowledge driven composite designoptimization system to automate the composite design optimizationprocess and output of three dimensional (3-D) laminated compositedesigns which parametrically link laminates, plies and analysisroutines, these routines are developed with a product life-cycle viewwhich inserts heuristic information onto the object oriented structure.Preferably, object naming conventions would be used in the knowledgedriven composite design optimization system to help maintain efficientassociation between parameters of mating structures with knowledge tohelp define the associations and rules to process requirements withinthe product life cycle.

SUMMARY OF THE INVENTION

Based on the above and foregoing, it can be appreciated that therepresently exists a need in the art for a knowledge driven compositedesign optimization process and corresponding system which overcomes theabove-described deficiencies. The present invention was motivated by adesire to overcome the drawbacks and shortcomings of the presentlyavailable composite design and fabrication technology, and therebyfulfill this need in the art.

One object of the knowledge driven composite design optimization processaccording to the present invention is to provide a composite designoptimization process wherein all subroutines included in the process areparametrically linked to one another. According to one aspect of thepresent invention, the resultant composite laminate definition isparametrically refined down to the ply level.

Another object of the knowledge driven composite design optimizationprocess according to the present invention is to provide a compositedesign optimization process wherein "best practice" rules for compositelaminate design are incorporated into the individual subroutines of thecomposite design optimization process. According to one aspect of thepresent invention, the "best practice" rules are applied in apredetermined sequence to permit generation of at least one optimaldesign solution.

Still another object of the knowledge driven composite designoptimization process according to the present invention is to provide acomposite design optimization process wherein manufacturing constraintsfor a part are considered as soon after the part geometry is defined aspossible.

Yet another object of the knowledge driven composite design optimizationprocess according to the present invention is to provide a compositedesign optimization process wherein the ply connectivity betweenconstant thickness laminate regions included in a part is globallyoptimized for the part. Moreover, the composite design optimizationprocess beneficially generates optimal ramp or thickness transitionfeatures responsive to the globally optimized region connectivity.According to one aspect of the present invention, connectivity isoptimized for variables including part weight, ply size and overall partstrength.

Another object of the knowledge driven composite design optimizationprocess according to the present invention is to provide a compositedesign optimization process capable of presenting the intermediatestages of, and resultant, laminate design in several different formatsto facilitate understanding of the laminate design at the ply level byall members of the laminate design team.

A still further object of the knowledge driven composite designoptimization process according to the present invention is to provide acomposite design optimization process wherein intermediate stages of thelaminate design can be stored for later display and reuse. It will beappreciated that this feature according to the present invention permitsthe laminate design team to perform tradeoff studies during the laminatedesign. Moreover, this feature facilitates later update of the knowledgebase, e.g., the "best practice" rules.

The knowledge driven composite design optimization process andcorresponding system, particularly Parametric Composite Knowledge System(PACKS), advantageously addresses the high cost and cycle time ofcomposite laminate definition. It will be appreciated that one cause ofthis problem stems from the fact that there are currently many differenttools, i.e., programs, for design and analysis of laminates, none ofwhich is completely parametric or associative. All of these conventionaldesign tools have different models for the same part definition, thusduplicating data in some cases, and often creating new data (that theother tools have no knowledge of) in others. A secondary problem withthese conventional software tools is the lack of visualization outputsfor the composite laminate ply details, which permits manufacturingpersonnel to misinterpret engineering design intent and necessitatesrefinement or recreation of engineering data.

Advantageously, PACKS addresses these problems by creating oneparametric model for composite design and analysis which outputs a threedimensional (3-D) definition of the composite laminate at the ply level.The PACKS module preferably integrates several new or existing toolsinto one shell, linking the outputs from, for example, the UNIGRAPHICS(TM) CAD program module, an analysis database, e.g., a PATRAN (TM)database, and the laminate designer subroutine while incorporating anumber of rules of laminate design to increase the speed of thecomposite definition process. Beneficially, data developed by PACKS canbe fed directly into manufacturing and analysis databases, or preferablyis linked into a common database which feeds all processes.

These and other objects, features and advantages according to thepresent invention are provided by a knowledge driven composite designoptimization process for designing a laminate part. Preferably, theprocess includes steps for generating a globally optimized plydefinition for a laminate part, and modifying the ply definition toinclude features of the laminate part, where the generating andmodifying steps are parametrically linked to one another and areperformed in the recited order as a "best practice", yet are notrestricted to this order. According to one aspect of the presentinvention, the generating step includes substeps for determiningconnectivity between a plurality of regions defining the laminate part,subsequently generating ramp features detailing interconnection of theregions defining the laminate part, and displaying views andcorresponding tabular data describing the laminate part and illustratingboth inter-region connectivity and the ramp features as specified by auser.

These and other objects, features and advantages according to thepresent invention are provided by a laminate part constructed using aknowledge driven composite design optimization process including stepsfor generating a globally optimized ply definition for a laminate partusing predetermined optimal rules of laminate design practice, andsubsequently modifying the ply definition to include features of thelaminate part, wherein the generating and modifying steps areparametrically linked to one another.

These and other objects, features and advantages according to thepresent invention are provided by a knowledge driven composite designoptimization process for designing a laminate part contained within aparametric composite knowledge system (PACKS) for generating a globallyoptimized ply definition for a laminate part in accordance with laminatedesign transition rules, and including a feature module for modifyingthe ply definition to include features which locally modify the globalply solution, wherein PACKS and the features module are parametricallylinked to one another, and wherein the knowledge driven composite designoptimization process is executed in PACKS and may be refined with thefeatures module. According to one aspect of the present invention, PACKSpreferably includes a connectivity subroutine for determiningconnectivity between a plurality of regions defining the laminate partresponsive to the transition rules, a ramp definition subroutine forgenerating ramp features detailing interconnection of the regionsdefining the laminate part, and a visualization subroutine fordisplaying views and corresponding tabular data describing the laminatepart and illustrating both inter-region connectivity and the rampfeatures as specified by a user.

These and other objects, features and advantages according to thepresent invention are provided by a knowledge driven composite designoptimization system used in designing a laminate part, including a firstdevice for generating a globally optimized ply definition for thelaminate part in accordance with laminate design transition rules,wherein the first device includes a second device for determiningconnectivity between a plurality of regions defining the laminate partresponsive to the transition rules, a third device for generating rampfeatures detailing interconnection of the regions defining the laminatepart, and a fourth device for displaying views and corresponding tabulardata describing the laminate part and illustrating both inter-regionconnectivity and the ramp features as specified by a user. Moreover, theknowledge driven composite design optimization system includes a fifthdevice for modifying the ply definition to include features whichlocally modify the global ply solution. Preferably, the first throughfifth devices are parametrically linked one to another, and the firstthrough fifth devices operate in numerical order.

These and other objects, features and advantages according to thepresent invention are provided by a computer memory storing computerreadable instructions for permitting a computer system to generate adesign for a laminate part, the computer readable instructions includinga parametric composite knowledge system (PACKS) for generating aglobally optimized ply definition for a laminate part in accordance withlaminate design transition rules, PACKS includes a connectivitysubroutine for determining connectivity between a plurality of regionsdefining the laminate part responsive to the transition rules, a rampdefinition subroutine for generating ramp features detailinginterconnection of the regions defining the laminate part, and avisualization subroutine for displaying views and corresponding tabulardata describing the laminate part and illustrating both inter-regionconnectivity and the ramp features as specified by a user, and furthercomprising a feature module including a subroutine for modifying the plydefinition to include features which locally modify the global plysolution, wherein PACKS and the features module are parametricallylinked to one another, and wherein PACKS and the features module areoperated in that order as a "best practice".

These and other objects, features and advantages of the invention aredisclosed in or will be apparent from the following description ofpreferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments are described with reference to the drawingsin which like elements are denoted by like or similar numbers and inwhich:

FIG. 1 is a high level conceptual flowchart illustrating a conventionalanalysis method employed during the composite design process;

FIG. 2 is a high level conceptual flowchart illustrating a knowledgedriven composite design optimization process according to the presentinvention;

FIG. 3 is a table comparing the material property characterizationsassociated with the flowcharts of FIGS. 1 and 2;

FIG. 4 illustrates local and global laminate optimization according tothe methods of FIGS. 1 and 2, respectively;

FIG. 5 illustrates the advantages of the composite cross sectiongenerated in accordance with the flowchart of FIG. 2;

FIG. 6 illustrates the advantages of the analysis method of FIG. 2 overthe conventional analysis method of FIG. 1;

FIG. 7 is a low-level block diagram of the knowledge driven compositedesign optimization process according to the present invention;

FIGS. 8A and 8B collectively form a low-level block diagram of theParametric Composite Knowledge System (PACKS) employed in the blockdiagram of FIG. 7;

FIGS. 9A and 9B collectively depict a first alternative subroutine forestablishing ply connectivity in PACKS described in FIGS. 8A and 8B;

FIGS. 10A and 10B together demonstrate a second alternative subroutinefor establishing ply connectivity in PACKS described in FIGS. 8A and 8B;

FIGS. 11A and 11B collectively illustrate a third alternative subroutinefor establishing ply connectivity in PACKS described in FIGS. 8A and 8B;

FIGS. 12A and 12B collectively show a fourth alternative subroutine forestablishing ply connectivity in PACKS described in FIGS. 8A and 8B;

FIG. 13 depicts a fifth alternative subroutine for establishing plyconnectivity in PACKS described in FIGS. 8A and 8B;

FIGS. 14A-14D collectively illustrate a subroutine for extending plyboundaries at the ply level according to PACKS depicted in FIGS. 8A and8B;

FIGS. 15A through 15C altogether depict a first alternative subroutinefor modifying critical laminate boundaries, within PACKS, as illustratedin FIGS. 8A and 8B;

FIG. 16 illustrates a second alternative subroutine for modifyingcritical laminate boundaries within PACKS, as depicted in FIGS. 8A and8B;

FIG. 17 is a detailed flowchart of the subroutine corresponding to step14 in FIG. 7 which advantageously can be employed to incorporate featureinformation into the globally optimized laminate design;

FIG. 18 illustrates the principle whereby plies are dropped betweenregions according to the present invention;

FIG. 19 illustrates the principle of global ply extension according tothe present invention;

FIG. 20 illustrates a ramp feature developed using global ply extensionaccording to the present invention;

FIG. 21 illustrates application of one of the "best practice" rules inaccordance with the present invention; and

FIGS. 22-37 depict various aspects of the user interface of a knowledgedriven composite design optimization system according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The knowledge driven composite design optimization process according tothe present invention was developed as a response to the inefficienciesnoted in the conventional composite design process, which was describedin detail above. These inefficiencies were discovered during the processflow evaluation. The process according to the present inventionovercomes these deficiencies by building a single data structure for thecomposites definition that expands the current Design, Manufacturing andProducibility Simulation (DMAPS) goals for parametric design ofcomposites and then refines the parametrics within the compositelaminate definition to the ply level. This is the first key facet of thepresent invention, since plies are the lowest entities the manufacturingshop handles. Many of the errors that occur during the manufacturingprocess are due to the lack of understanding of ply location inthree-dimensional (3-D) space and how these plies change (propagate orterminate) throughout the overall laminate structure. It will beappreciated that linking analysis and manufacturability to geometry atan early phase in the composite design process is an innovation allowedby designing to the ply level, which cannot be duplicated usingconventional composite design techniques.

To integrate knowledge, a process must be consistently followed to knownoutcomes which meet "acceptable" user practices today. Advantageously,the present invention includes methodologies, hereinafter referred to asdecision tracking methodologies, which yield results typically selectedby users. The selection of standard options, order of selection, and thereference in which they are selected, also referred to as domain, aretracked using these decision tracking methodologies to (1) enable growthof the process and (2) identify areas for improving or streamlining thedesign process through the implementation of a "best" practice. Thedecision tracking methodology according to the present inventionadvantageously can enable a determination of which choice and in whatorder of selection yields the best results in the least number ofiterative steps. As such, the knowledge driven composite designoptimization process not only offers an improved way to designcomposites by capturing today's knowledge database, but also offers amechanism for expanding that knowledge base through use of the compositedesign optimization process.

The knowledge driven composite design optimization process according tothe present invention preferably is initiated when the design teamconceptualizes the new part geometry. Like the conventional compositedesign process, the first physical definition is initially describedusing a thickness map by which laminate families are identified. Thepresent invention departs from the conventional composite design processat this point by focusing on the details of the plies immediately afterthese first assessments are made as illustrated in the flowchart of FIG.2.

Advantageously, focusing on the details of the plies forces the designteam to immediately consider constraints of "reality", i.e.,manufacturability, for a specific thickness, as illustrated in FIG. 3.As shown in FIG. 3, which illustrates one of the novel features of theknowledge driven composite design optimization process, the conventionaldesign process focuses on the thickness of a single laminate partwithout consideration or understanding of the fact that there are alimited number of potential laminate families with material propertiesappropriate for the thickness of the material. As mentioned inconnection with FIG. 1, the design team does not considermanufacturability until the later steps of the design process. Moreover,the focus on individual regions of constant laminate definition, withoutany attempt to consider laminate similarities in adjacent regions ofconstant laminate definition, leads to a large number of plyterminations within the composite part and, thus, poor connectivitybetween adjacent regions of constant laminate definition, as illustratedin FIG. 4. In contrast, focusing on the details regarding ply thicknessearly in the design process allows the impact of ply "connectivity"across regions to be examined in detail; this advantageously forces boththe designer and the analyst to consider the same basic model.

The focus on the connectivity between regions of constant laminatedefinition identifies two more key aspects of the composite designoptimization process: (1) consideration of which ply or plies within thestack terminate or continue; and (2) consideration of how changing theorder of stacking within a region or regions can impact both the overalloptimization process in other mating regions as well as the strengthlevel of the composite laminate. It will be appreciated that the impactson manufacturability and the overall strength of the laminate panelswith respect to decisions regarding connectivity are extensive.

This portion of the process, i.e., the connectivity subroutine,establishes the order of manufacturing lay-up, size of the plies, andbasic component weight. Iterations on connectivity are completed tooptimize for three basic variables, minimum weight, largest ply size andacceptable strength. The most significant outgrowth of this ply levelfocus is that the inner moldline of the part is derived as a naturalconsequence of the process rather than defined as a separate entitythrough geometrical manipulation of the single plane projections as inthe conventional process. This connectivity subroutine describes whatcan be referred to as the conceptual phase of the composite definitionprocess. The outputs of this new conceptual phase are significantly moredetailed than are conventionally completed in industry for a compositedefinition.

Advantageously, the inner moldline of the laminate part can be derivedthrough this knowledge driven composite design optimization process byvirtue of the use of a disciplined process and parametrics, combined inan environment that encourages, or at least allows, reuse of the designdata and produces a consistent design output. It will be noted thatparametrics are extensively used today by industry to allow reuse ofengineering information. It should also be mentioned that parametricshave never been applied to composites at the ply level, which is evidentfrom the references briefly discussed immediately below.

First, it should be mentioned that the paper entitled "The A.S.U.Features Testbed: An Overview" by J. Shah, M. Roger, P. Sreevalsan, D.Jsiao, A. Mathew, A. Bhatnagar, B. Liou, and D. Miller, Department ofMechanical and Aerospace Engineering, Arizona State University, pp.233-241, describes a decade's worth of feature based design work.Definition of common terms like feature, feature hierarchy, attribute,compound feature, generic vs. instanced feature, parameter inheritance,geometric model, feature model, definition methodology, featurevalidation, feature interactions, and modeling shell are presented. Itwill be appreciated that this paper describes the theories that makefeature based geometric reasoning function.

In one approach to laminate design discussed in a paper entitled "AnExpert System for the Design and Analysis of Composite Structures" byBarry Davidson, Utpal Roay and Chris Ludden, Department of Mechanical,Aerospace and Manufacturing Engineering, Syracuse University, Syracuse,N.Y., Presented at "Rotorcraft Composite Manufacturing: Transition intothe 21st Century," Sep. 21-23, 1993, the approach was limited in itsability to consider anything but flat plate geometry. The authors focusstrictly on analysis selection of an optimal lay-up for a given designcondition and a completely knowledge-driven search for possiblesolutions. It will be appreciated that this aspect is embodied in thecomposite design optimization process according to the present inventionin the "laminate designer" subroutine, which is a minor feature of thepresent invention. The described analysis selection of an optimal lay-upincreases the speed of the review for numerous analytical solutions.However, it is not unique or developmental; it is only the rapidapplication of textbook analysis routines. In contrast, the knowledgedriven composite design optimization process according to the presentinvention includes both preliminary and final (optimized) loops foranalysis refinement. This unique aspect of the present inventionfacilitates the tight integration of geometry, using parameters for easeof update and sensitivity tracking, and the decomposition of thelaminate to the ply level for refined visibility and sensitivity. Theply level integration allows the design team to integratemanufacturability into the analysis decision making process. This levelof refinement is critical to achieving affordable and manufacturabledesigns. Moreover, without visibility into the details and/or featuresbeyond the preliminary level, the system as described by Davidson et al.is limited and, thus, useful by single discipline users at best.

The paper "A Knowledge Based Expert System for Laminated Composite StrutDesign," by C. Wu, Department of Applied Mathematics, City Polytechnicof Hong Kong, J. Webber, Department of Aerospace Engineering and S.Morton Department of Mathematics, University of Bristol, published inAeronautical Journal, January 1991, addresses a more practical designprocess, i.e., gets closer to reality, by considering more geometricshapes. However, the approach does not integrate or link design andanalysis "real geometry," only generic representations. Moreover, thepaper focuses mainly on analysis and optimization of the compositelaminate. No decomposition or detailed assessments at the ply level areincluded. No manufacturability knowledge is included. No final designsare created with geometry. Thus, the paper merely describes ananalytical tool. Thus, while the paper describes the theory for handlinguncertainty in the design process, a truly practical design can only beprovided by integrating multi-disciplined knowledge into the analyticaloptimization process along with geometric reasoning and visualization.See also, "Bolted Joints in a Laminated Composite Strut Design ExpertSystem" by C. Wu, Department of Aerospace Engineering, University ofBristol, UK, published in COMPOSITE STRUCTURES 22 (1992) pp. 63-85.

In "Trends in Engineering Software and Hardware--Knowledge-Based ExpertSystems in Structural Design," D. Sriram, M. Maher, S. Fenves, CarnegieMellon University, published in Computer & Structures Vol. 20, No. 1-3,pp. 1-9, 1985, the current state of knowledge systems is reviewed. Thepaper attempts to describe an idealized system yet offers no applicationspecific information and identifies no tool capable of achieving thegoals outlined. Furthermore, "Analysis of Design Abstraction,Representation and Inferencing Requirements for Computer-aided Design"by Jami Shah, Mechanical and Aerospace Engineering, Arizona StateUniversity, and Peter Wilson, General Electric Company, Schendectady,N.Y., discusses laminate design from a focus of CAD systems, i.e., asystem for documentation, drafting and specification of nominal geometryfor finite elements and NC. The authors also describe the application ofan expert system to design as lacking a sound geometry basis; theauthors also limit their application to specific domains. Theshortcomings identified by the authors are solved by the presentinvention, due to the present invention's characteristic focus ongeometry integration for visualization along with the use of engineeringknowledge throughout the definition process.

The paper entitled "An Expert System for Laminated Plate Design UsingComposite Materials" by J. Webbei and S. Morton, Department of AerospaceEngineering and Mathematics, University of Bristol, Bristol, U.K.,published in COMPUTERS AND STRUCTURES, Vol. 37, No. 6, pp. 1051-1067,1990, discusses the need for an expert system and its benefits forcomposites. The focus of this discussion is also on analysis, in thatthe authors identify the need to describe macroscopic mechanicalproperties which characterize the microscopic lack of uniformity ofcomposites. The authors do not discuss geometry or have a system planthat is based upon the integration of geometry and analysis; the authorsmerely offer basic fundamentals taught by all universities to selectoptimum design in a single discipline design environment. This approachis not used in practice. In contrast, the knowledge driven compositedesign optimization process according to the present invention usesmulti-disciplined knowledge in the system to assist the user insensitivity assessments which identify key rules and impacts of changingthem. Moreover, this design process uses the geometric parameters tolink design, analysis and manufacturing requirements. This, in itself,is a novel feature of the present invention.

"Optimum Design of a Composite Structure with ManufacturingConstraints," by D. Costin & B. Wang, Dept. of Mechanical Engineering,University of Texas at Arlington, published in Thin-Walled Structure V17(1993), pp. 185-202, describes computer programs which producemulti-disciplinary optimization as expensive or impossible to produce.It should be mentioned that this work is of limited usefulness becauseof its limited focus to the laminate level analysis. The manufacturingconstraints identified in this paper are limited to controlling the rateof thickness change between wing zones to control twists. This is notthe most significant manufacturing constraint, although it is a validone. The authors ignore ply level manufacturing constraints which arethe true drivers of balanced "weight optimum and buildable" compositestructures. The present invention incorporates an understanding that plycontinuity is a key manufacturing constraint. Moreover, the authorssuggest that their selected (optimum) designs are buildable, even thoughgeometry was not integrated into the process. It will be appreciatedthat the buildable part had to be manually defined after the analysisprocess was completed, according to this reference.

In addition, the article entitled "Top-Down Construction of 3-DMechanical Object Shapes from Engineering Drawings," by H. Yoshiura,Hitachi Research Laboratory, K. Fujimura and T. Kunii, University ofTokyo, published in COMPUTER IEEE Journal, 1984, pp. 32-40, focuses onthe need for a more efficient method for carrying out operations betweenobjects such as intersections because the man/machine interface is thelargest productivity obstacle in CAD/CAM systems. Thus, the articlefocuses on interpretive 2-D knowledge of "natural language" toautomatically create 3-D drawings. The authors do no work usingknowledge systems; the authors create a solid given a 2-D drawing.According to one aspect of the present invention, a 2-D drawing iscreated once the system is given a 3-D definition. It should bementioned that the hard part is facilitating the automatic developmentof the design; the documentation of the optimum design is relativelyeasy. Furthermore, the authors do not use parametrics in their work, nordo the authors care about associations between features and objects.

In "Interfacing Solid Modeling to CAD and CAM: Data Structures andAlgorithms for Decomposing a Solid," by T. Woo, University of Michigan,Published in December 1984 issue of COMPUTER, pp. 44-49, decompositionis referred to as the disjoint condition for solid elements of geometryof non-overlapping simplices. This is important for modeling in CAD/CAMsystems. In contrast, the term decomposition according to the presentinvention refers to the parametric relationship between the compositelaminate and the composite plies that are employed in fabricating thelaminate. This paper also discusses the use of separation of geometryand topology to permit separate geometric processing and topologicalprocessing. This is an inherent feature in all modem CAD/CAM systems.

The paper entitled "Representation of Geometric Features, Tolerances,and Attributes in Solid Modelers Based on Constructive Geometry", by A.Requicha, Senior Member IEEE and S. Chan, published in IEEE Journal ofRobotics and Automation, V RA-2, No. 3, September 1986, pp. 156-166,describes the limitations of Constructive Solid Geometry (CSG) modelersto integrate tolerancing, surface finish and other data that specifyallowable inaccuracies of nominal geometry. It also describes how thesevariational data reflect the intended function of the described geometryrepresentative of metallic designs, primarily. Various schemes ortheories for integrating solid feature information into a modeler arealso described in the paper. The limitations discussed in this paper arestill present in all conventional modeler packages. Various knowledgebased systems are attempting to bridge these gaps but none have beensuccessful to date. These deficiencies prevent automatic planning,inspection and assembly operations from operating in the CADenvironment. Simulation tools are attempting to bridge the gaps, yet arestill immature.

Finally, the paper entitled "Memory Driven Feature-Based Design," by Y.Pao, F. Merat, G. Radack, Case Western Reserve University, ElectricalEngineering and Computer Science, January 1993 (WL-TR.93-402 1),documents the Rapid Design System (RDS) under development at theMaterials Directorate of Wright Laboratory. In particular, the modulararchitecture of the system is described. It should be noted that thegoals of the system described in this paper are closely related to thegoals according to the present invention; however, the paper focuses onthe manufacturing aspects for automation, learning "neural-net"associative memories, storage and retrieval approaches. In that respect,the system description shows the commonality of approach for knowledgesystems.

It should be mentioned that all of the above-identified articles areincorporated herein by reference for all purposes to the maximum extentpermitted. It should also be noted that the commonality of knowledgesystem architecture does not minimize or trivialize the significance ofthe selected approach for the inventive Knowledge Driven CompositeDesign Optimization Process and corresponding System. The unique aspectsincluded in the composite design optimization process of the presentinvention address how various pieces are integrated with detailedknowledge developed to convert the 2-D information typically found infabrication facility document data and produce 3-D designs while, at thesame time, providing an insight into ply level details. By capitalizingon the traceability available with the use of parametrics, associativityand object relationships are tailored specifically to produce a robustproduct with automatic and manual override modes of operation. Theincorporation of refined knowledge at the appropriate design steps is akey element needed for effective operation of the knowledge drivencomposite design optimization process and corresponding system. It willbe appreciated that a similar system architecture would not inherentlyproduce the same type of output or design efficiency in a compositedesign system.

As mentioned in the discussion immediately above, the composite laminateaccording to the knowledge-driven composite design optimization processadvantageously can be controlled by global parametrics. Normally, theinherent termination and build-up of plies in a composite laminatecreates a feature called ramp which is controlled by a mathematicalrelationship between the ply thickness and the laminate thickness,called a ramp ratio. In the knowledge driven composite designoptimization process, the locations of the ramps are beneficiallydefined after connectivity is established by extending the plies in aspecific order. It should be mentioned that fabrication facilities oftenhave several, e.g., three, standard extension methods any one of whichcan be selected based upon manufacturing preferences. The level ofdiscipline in the process and parametrics allow the composite designoptimization process and corresponding system to identify manufacturingmethod specific variations of a geometric feature and tie the resultantply level design to the process. This is also a major departure fromcurrent composite design methods. It will also be appreciated that thisrepresents reduction to practice of a significant part of the designtheory discussed in the literature, such as that briefly discussedabove, for feature-based design of metallic composites.

It should be mentioned that a missing element of all the theoreticaldiscussions for metallics and composites is how to develop a processproviding the needed knowledge for optimal design in the best sequenceto reduce the size and complexity of the optimization process. Byfocusing on plies earlier in the process, numerous iterations betweendesign and strength advantageously can be eliminated. The new knowledgewhich was developed during the refinement of the knowledge drivencomposite design optimization process is related to how the designpractices impact three-dimensional ply geometry. One such step, whichhas been identified as critical to the conceptual design process, is touse the "thickest" region within an optimization run while using the"thinnest" region to bracket the boundaries of the stacking sequence.More specifically, if the thinnest region is fully contained within thethickest region, then the intermediate thickness regions can be modifiedto ensure a highly manufacturable connectivity solution. See FIGS. 5 and6, wherein FIG. 5 illustrates the advantages to the design team ofhaving visual displays of the cross section of the laminate at the plylevel and FIG. 6 contrasts the conventional laminate stacking sequencedefinition with the laminate designer subroutine according to one aspectof the present invention.

It will be appreciated that this methodology, which is conceptuallypresented in FIGS. 2-6, can easily be extended to allow successiveiterations, e.g., from the thickest region to a thick region, from athick region to a thin region, and from a thin region to the thinnestregion. This methodology has been found to work on all evaluations ofcomposites designed for F/A-18, C-17, and T-45 aircraft programs.

The number of possible combinations in the stacking sequence can bevastly reduced by realizing that it is preferred to build laminate partsthat have a centerline symmetric ply definition. This is because thenumber of stacking sequences has an exponential relation to the numberof independent plies, i.e., the number of possible stacking sequences isequal to the number of ply orientations raised to the power of thenumber of plies (orientations ^(plies)). For centerline symmetriclaminates the number of independent plies is approximately one half thatof unsymmetric laminates, thus the exponent is reduced by a factor ofapproximately two. Advantageously, this number can be reduced further byimplementing the realization that it is also preferable to employbalanced laminates, i.e., laminates with equal numbers of plus and minusorientation angled plies. Beneficially, additional knowledge exists inthe form of guidelines: (1) detailing how many plies can be dropped in alocation; (2) which ply orientations can be located next to another plyorientation; and (3) how many plies of any particular orientation can belocated together. By using this information at the earliest possiblestep in the composite design optimization process, rework andredefinition advantageously can be minimized.

It should be mentioned that this latest group of the knowledge to beintegrated into the composite design optimization process was taken fromthe standard practices of a single design and fabrication facility. Itshould also be noted that the composite design optimization process alsobracketed the variance in a family allowed when transitioning betweenregions for tighter control of strength variation within the part.

The secondary features of the composite design optimization process andcorresponding system advantageously include the characteristics neededto make the process robust while keeping the process tailorable for thespecific functional requirements of any particular part. These secondaryfeatures include refinements to the basic laminate definition. Morespecifically, the secondary features typically create only local changesin the laminate, primarily in the form of cutouts, i.e., holes,build-ups for fasteners, i.e., pads, and load transition regions such asstep lap joints, etc. The knowledge regarding secondary features at theply level provides a fundamental key to design reusability.

The specific steps of the knowledge driven composite design optimizationprocess according to the present invention will now be described withreference to FIGS. 7-17, which collectively depict a series of step-downflowcharts, with increasing depth of discussion between FIGS. 7 and 8,respectively. FIGS. 9-16 illustrate details and alternative subroutineswhich advantageously can be employed in the flowchart of FIGS. 8A and 8Bwhile FIG. 17 expands upon a step employed in the flowchart of FIG. 7.

Before looking at FIG. 7 in detail, it should be mentioned that it isthe composite design optimization process, taken as a whole, whichprovides the true advantages with respect to composite design processes.Whereas conventional composite design endeavors utilize many stepssimilar to those of the knowledge driven composite design optimizationprocess according to the present invention, these conventional stepswere implemented in only a haphazard and ambiguous way, if theseconventional steps were implemented at all. As illustrated in thecomposite design optimization process overview of FIG. 7, the presentinvention establishes how and where the specific revisions to theconventional design process occur.

In the analysis optimization, it is necessary to introduce propertiesfor actual, manufacturable global laminates. This is outlined in detailin FIGS. 8A and 8B, and in the subsequent flowcharts of FIGS. 9-16.FIGS. 8-16 illustrate the key innovation of establishing 3-D plies,i.e., designing to the ply level. Since connectivity, i.e., determininghow the plies in a local laminate connect to the plies in adjacent locallaminates, is crucial to establishing 3-D plies, it will be noted that atotal of five distinct subroutines for establishing the connectivity arepresented in FIGS. 9A-13. It should be mentioned that these subroutinesof the knowledge driven composite design optimization process have beendeveloped to produce laminates which follow certain rules of "best"practice, such as distributing ply terminations and terminating pliestoward the centerline whenever possible. Within these five subroutines,there advantageously can be a tremendous number of potential variationsin the plies allowed, since the designer can freely select from thevarious subroutines to be performed. Thus, the designer has theflexibility to perform tradeoff studies to identify preferredconnectivity solutions while tracking the specific method by which eachsolution was obtained. It will be appreciated that this innovativecharacteristic allows improved documentation of the composite designoptimization process.

Although most features are defined in subsequent operations, as will bedescribed later, ramps are an integral feature of every ply and thus arecalculated with the base laminate. Ramps are produced because theoccurrence of more than one ply termination at a specific location isnot a good practice. Rather, the plies are extended slightly such thatthe ply terminations form a gradually sloping thickness transition. Totruly design to the ply level, one must establish which ply boundariesshould be extended to create these ramps. The subroutine needed todefine these extended boundaries is outlined in FIGS. 14A-14D. Thissubroutine embodies several alternative methods for extending plies,depending on the requirements and geometry of the component. Again, theinnovation lies in the systematic and well-defined approach whichensures a consistent and trackable extension mechanism.

Attempts at laminate optimization described in the open literature failto realize that one cannot optimize every local laminate if aneconomically manufacturable component is required. It is a wasted effortto optimize each piece, without consideration for how the pieces fittogether. These local optimizations are used judiciously with the newapproach identified within this process, called Transition Rules, toachieve an optimal global solution. Connectivity using the methodsdescribed previously is powerful, yet it is merely a shadow of the powerpossible by redefining local stacking sequences to achieve optimal,manufacturable ply definitions. The process for this is also outlined inFIGS. 9A-16 and will be referred to as Transition Rules.

Connectivity attempts to join existing local laminates in the best waypossible. Transition Rules, on the other hand, redefine the locallaminates into specific patterns to ensure optimal connectivity. Itshould be mentioned that these techniques have never been outlinedpreviously. One innovative canon of the knowledge driven compositedesign optimization process is in the realization that if successivelythinner laminates only contain plies contained in thicker laminates,then one can be assured that the thinner laminates will connect well tothe thicker laminates. It will be appreciated that one can vary theoutcome of the Transition Rule by varying the starting and endinglaminates. Moreover, the outcome of the Transition Rule will be affectedby varying key parameters governing the rule, e.g., varying the numberof adjacent terminations allowed, varying the family characteristics,and varying the number of continuous plies at either moldline orcenterline, or both. Thus, the designer advantageously has the controlof the composite design optimization process needed to conduct tradeoffstudies while maintaining a trackable path to document the overalldesign process. It should be mentioned that the starting and endinglaminates can be modified either by hand, by interacting with externalcodes, or by local optimization performed using the so-called laminatedesigner subroutine, as will be discussed in greater detail below withrespect to FIGS. 15A-15C and 16. It should also be noted that theLaminate Designer process is also an innovation, allowing all familiesand stacking sequences within a given range to be evaluated in order tooptimize the local stacking sequence. Although this can be atime-consuming process, the process becomes feasible because the processis only performed for critical regions of the overall design.

The final innovations are outlined in FIG. 17. It will be noted that,first and foremost, the process flowchart illustrates a subroutine bywhich local features, e.g., holes, are incorporated into the globallaminate only after the basic global laminate advantageously has beendefined. One of ordinary skill in the art will appreciate that this ispossible because, while each feature affects the global laminate, eachfeature affects the global laminate only locally. Thus, the designerpreferably is able to define a set of rules governing the behavior ofeach specific feature, e.g., how the incorporation of a particularfeature into the overall design will affect the global laminate.

The remaining innovations in the knowledge driven composite designoptimization process involve manufacturing; the composite designoptimization process includes specific requirements for ensuringmanufacturability in the knowledge driven composite design optimizationprocess flowcharts. It will be understood that separate databases arecurrently being used for tooling, ply flattening, i.e., projection ofthe as-laid-up plies onto planes to determine the cut shape prior tolay-up, ply nesting, laser projection, wherein outlines of theindividual plies are projected onto the tool surface during lay-up tofacilitate proper alignment, ply cutting, and the creation ofmanufacturing drawings. This occurs because each group involved in theoverall design and fabrication effort uses different variations of thedata, i.e., none of the groups consider the actual plies. Designingcomposites to the ply level, which necessitates using the outlinedknowledge driven composite design optimization process, enables all ofthe data required for each of these distinct operations to be stored toand retrieved from a single database.

As discussed above, a knowledge driven composite design optimizationsystem would be beneficial in reducing the manual work of the design andanalysis team and in allowing the team to develop an understanding ofthe benefits of knowledge driven systems. A secondary advantage of theknowledge driven composite design optimization system is in organizingthe knowledge required for feature-based design of composites usingparametrics with a focus on:

(1) Composite laminate design;

(2) Documentation of ply organization;

(3) Decomposition of a laminate into composite plies in 3-D space;

(4) Automated section cut creation at interactively picked locations;and

(5) Automated drawing presentation.

It should be mentioned that the knowledge driven composite designoptimization software, which advantageously can be stored on a recordmedium, e.g., a hard disk or CD-ROM, beneficially converts a generalpurpose computer system, such as that running a conventional CADprogram, into a special purpose computer system, i.e., a knowledgedriven composite design optimization system. Hereinafter, the term"system" will be used to designate both the composite designoptimization software program and the special purpose computer systemrunning the composite design optimization software program.

Preferably, the knowledge driven composite design optimization system isa feature-based, parametric, knowledge-based system for designautomation of composite laminates, which incorporates a geometricalreasoning engine supported by a knowledge-base to automate the designand layout of the plies based upon the surface geometry and theassociated structural loads. The input to the system preferably includesthe external surface geometry of the part or panel, and the associatedfinite element model, along with the internal loads computed as a resultof the applied loads.

The knowledge driven composite design optimization system advantageouslycan be organized in two modules or program blocks that perform thevarious functions leading to the composite plies parametrically definedand located in 3-D space, in addition to the computation of geometry forthe bounding surfaces to facilitate data transfer to manufacturingactivities. The composite design optimization system preferablyimplements composite laminate design rules along with interfacesenabling electronic access to help, additional information, and advice.It should be mentioned that the user retains the ability to overrideoptimization logic and warnings through the user interfaces.

Referring to FIG. 7, an overview of the composite design optimizationprocess will now be presented in detail. The process according to thepresent invention starts with step 1, in which basic design requirementsare defined and step 2, in which the structural concept definition forthe part takes place. During step 3, the design space itself isdesigned, thus limiting the possible portion of total design space fromwhich an optimal design solution can be obtained. Moreover, during step4, meshable geometry is created and, during steps 5 and 7, the meshablegeometry is loaded into a database, e.g., the Design, Manufacturing andProducibility Simulation (DMAPS) database.

In parallel with updating the DMAPS database, the mesh geometry isprepared for finite element analysis (FEA) during step 6. Afterwards,historical loads, geometry information, and material properties areapplied to the prepared mesh geometry during step 8 and global FEAoptimization with respect to thickness distribution is performed duringstep 9. Subsequently, global beam and panel optimizations advantageouslyare performed during step 10. Preferably, the Parametric CompositeKnowledge System (PACKS) module, i.e., the subroutine wherein the designof a manufacturable component with graphical interrogation is performed,receives the results of the optimization processing from step 10 andestablishes 3-D plies in step 11, as discussed in greater detail below.The composite design optimization process then advances to step 12.

During step 12, a global ply definition is defined. The process thendetermines whether the design is optimized in step 13. If the answer isnegative, the process updates the FEA mesh using new properties and/orparameters during step 18 and loops back to the start of step 9. Whenthe answer at step 13 is affirmative, an additional subroutine of PACKSis performed, wherein features are incorporated, the mesh geometry isupdated and a build-to data package is generated during step 14. Duringsteps 15 and 16, the database properties advantageously are modified andthe DMAPS database is updated, respectively. Lastly, the parametricgeometry model preferably is updated during step 17.

In short, the initial laminate definition for the part or panel iscalculated from the finite element model mesh with base system rules forconnectivity. After viewing this laminate, the user can makemodifications to the laminate. These modifications allow the user to tryseveral scenarios, analyze alternatives to the input laminate, or simplyrefine the original design without starting the finite element anddrafting/design processes over again.

The PACKS module, which is invoked at step 11, requires three inputs,which contain the definition of the geometry, materials, and laminatearrangements for a given project. In addition, a fourth, optional inputis the loads file resulting from analysis of the finite element analysis(FEA) mesh. Preferably, the design surface or geometry, i.e., the outermoldline of the laminate, can be provided as a UNIGRAPHICS (TM) NURB-128or an IGES-formatted file. It will be appreciated that these fileformats are well known to one of ordinary skill in the art; furtherdiscussion of file formats will be omitted. Moreover, the laminatedefinition includes the laminate geometry, ply stacking sequence, plymaterials, (and hence thickness), and ply orientation. Advantageously,the laminate definition can be obtained from the finite element modelmesh. Preferably, the FEA mesh defines the geometry of each element inthe laminate stack, gives the ply stacking sequence used in theanalysis, and provides references for each of the coordinate systemsused in the file. To maintain a consistent database within the analysis,the knowledge driven composite design optimization system advantageouslycan obtain all required information from the analytical database, e.g.,a PATRAN (TM) database, directly. This will ensure correlation torelated versions of the finite element model. The system will record thefilename and date of the source file in the analytical database so thatthe user will know the source of the original laminate definition.

Other input capabilities can be included in the knowledge drivencomposite design optimization system. For example, a sketcher inputsubroutine can be included to allow the user to draw the laminatedefinition instead of obtaining it from the FEA mesh. Moreover, the useradvantageously can input region boundaries from the UNIGRAPHICS (TM) CADprogram as part of the laminate definition. Furthermore, the internalloads obtained from the NASTRAN (TM) finite element solution can beretrieved from a direct query of the analytical database. It will benoted that the elements in the loads preferably correspond to theelements defined in the FEA mesh. It should also be mentioned that thisinput is required only when the user wishes to visualize the loaddistribution or use the laminate designer subroutine, discussed ingreater detail below, for stress checks.

Advantageously, in order to provide for efficient use of the compositedesign optimization process and corresponding system, and to facilitatedebugging of errors in the input files, the system includes one or moresubroutines to verify the content and format of the input files.Specific checks include, but are not limited to, checking for thepresence of unsymmetrical laminates, the presence of gaps ordiscontinuous elements, the absence of required element properties,i.e., thickness, laminate definition, surface correlation, materialproperties, and coordinate references, as well as for consistency ofelement normals.

In order for the user to directly edit the laminate, the compositedesign optimization system advantageously allows the user to add,remove, or change a ply in the active model. The user may also modifythe ply's thickness, orientation, or material. Preferably, the compositedesign optimization system determines the effect of any direct edit onthe geometry of the other plies in the laminate, allowing the laminateto be regenerated automatically.

It will be appreciated by one of ordinary skill in the art that laminateregions are continuous sections of identical laminate definition. For aspecified region, the user advantageously can change the number ofplies, or the target family, i.e., the ideal percentages by volume ofthe different directional constituents in the laminate. Preferably, thelaminate family includes plies oriented at up to four orientations:zero; ninety; forty-five and negative forty five degrees from theirdefined zero axis, which axis is defined in the FEA data. Thus, alaminate family identified by the nomenclature "50/40/10" includes 50%0° oriented plies, 40%±45° oriented plies and 10% 90° oriented plies.The system advantageously allows the user to modify the new targetfamily by selecting a region and specifying the new target family orspecifying the target family for a number of regions at once.

Additionally, the user can edit transitions in the laminate familieswithin a component to achieve the target family or to minimize plyterminations. This function can be accomplished by incorporation ofrules for generating intermediate families given a description of astarting thick section lay-up and an ending thin section lay-up, and therules for ply transitions there between.

Laminate lay-ups within a region advantageously can be determined byselecting the whole ply solution which minimizes the average variancefrom the target family of that region. It will be appreciated that thevariance can be determined by computing the absolute difference inpercent content between each directional constituent and thecorresponding target. By default, the tool permits a 5 percent variancefrom each directional constituent in the target family. The userbeneficially may specify a different allowable variance. Preferably, thesystem also enforces a global minimum and maximum percentage makeup forall directional constituents in all regions, these values being 7percent and 55 percent, respectively, by default in an exemplary case.However, the user can freely input their own minimum and maximumpercentages.

Advantageously, a number of rules and best practices for sectionlay-ups, ply drop-offs, and ply extensions are incorporated into thecomposite design optimization system. These rules are generally enforcedduring laminate editing by the user, although some rules are fixed whileother rules may be overridden, customized, or even turned-off inaccordance with the user's current needs.

It should also be mentioned that all potential families for a givennumber of plies are determined by the knowledge driven composite designoptimization system and corresponding process. The family with the leastaverage absolute difference from the target is denoted the selectedfamily which controls the orientation of the plies that must terminatefrom the next thickest region. In the event that the target family for agiven region cannot be reached within the allowed variance, then thetool determines if the target can be reached by dropping fewer plies. Ifno acceptable family is found after the thickness is increased up to andincluding the thickness of the thickest adjacent region, then the useris presented with the following options:

(1) use the lay-up of the adjacent region;

(2) use the closest target outside the defined variance; or

(3) redefine the target and/or variance of the region in question.

Where transitions between two laminate regions are necessary, there arerules governing which plies should be terminated, and how far to extendthese plies prior to termination. These rules will be discussed ingreater detail below.

Referring specifically to FIGS. 8A and 8B, which collective illustratethe program module generally comprising step 11 in FIG. 7, PACKSadvantageously includes the fundamental steps for establishing the 3-Dplies used in the knowledge driven composite design optimization processaccording to the present invention. As discussed above, optimizationrequires the introduction of properties for actual, manufacturableglobal laminates, i.e., the key innovation of establishing 3-D plieswhich allows designing to the ply level. Since connectivity, i.e.,determining how the plies in a local laminate connect to the plies inadjacent local laminates, is crucial to establishing 3-D plies, itshould again be mentioned that a total of five distinct subroutines forestablishing the needed connectivity are presented in FIGS. 9A-13 anddiscussed in greater detail below. It should also be mentioned thatthese subroutines of the knowledge driven composite design optimizationprocess have been adapted to produce laminates which follow certainrules of "best" practice. Finally, it should be noted that these fivesubroutines are alternatives; the design team can freely select from thesubroutines. All of these variations, including a variation produced byselecting steps from among the alternative subroutines illustrated inFIGS. 9A-13, are considered to be within the scope of the presentinvention.

During step 100 of the subroutine of step 11, the surface, the materialdistribution of laminate families and the thickness of the laminateparts advantageously are designed while, during step 101, the model isqueried for geometry and materials. At step 102, the starting locationon the surface of the object being designed is established. During steps103 through 105, an iterative loop is established whereby all adjacentareas of identical laminate definition are connected into regions (step103), a determination as to whether the entire surface has been definedas the regions are made (step 104) and, when the answer at step 104 isnegative, a new starting location on the surface is established (step105), and the subroutine loops back to the beginning of step 103. Whenthe answer is affirmative, a starting region is established during step106.

During step 107, neighboring regions are queried to permit borders,which are defined as any boundary between two regions, to beestablished. At step 108, a determination is made as to whether or notthe borders completely define the starting region. When the answer isnegative, undefined regions are queried, segments are outlined andclassified as internal (cutout) or external (part boundary) edges duringstep 109. After step 109 has been completed, or in the event that theinquiry at step 108 is affirmative, the subroutine jumps to step 110 anda determination is made as to whether all region pairs have beenqueried. When the answer is negative, a new starting region isestablished (step 111) and the subroutine loops back to the beginning ofstep 107. When the answer is affirmative, the applied connectivityprocess advantageously is chosen during step 112.

Preferably, ply connectivity is established, i.e., defined, for existinglocal laminates during step 113. As mentioned above, determining theconnectivity between laminate panels entails specifying which ply orplies within each laminate stack terminate or continue and determiningthe impact of changing the order of stacking within a region or regions.It will be appreciated that the impact can be on both the overalloptimization process in other mating regions as well as on the strengthlevel of the composite laminate. It will be appreciated that the impactson manufacturability and the overall strength of the laminate panelswith respect to decisions regarding connectivity are extensive.

It should be noted that the choice for which of the plies will beterminated preferably is governed by the position of each of the plieswithin the laminate stack. In an exemplary case, the plies closest tothe centerline can be dropped first, within the constraints of thedefined number of continuous plies at the centerline. The default numberof centerline plies advantageously can be determined by a query ofselected thick and thin regions. If both of these regions are defined byan even number of plies, then the default number of centerline pliesbeneficially can be set to two. If either region is composed of an oddnumber of plies, then the default number of centerline plies preferablyis one. Moreover, the default number of continuous moldline plies can bedetermined by a query of the selected thin region. All plies which arenot continuous centerline plies in the thin region can be, by default,designated as continuous moldline plies. Thus, the specific defaultnumber of continuous moldline plies advantageously can be determined bysubtracting the number of continuous centerline plies from the number ofplies in the thin region, dividing the remained by two, and then usingthe closest integer number to this value. As a result, in a laminatecreated using the default values, all plies appearing in the selectedthin region are continuous throughout the laminate.

In the event that a significant number of plies are terminating betweenadjacent regions, the dropped plies advantageously can be distributedthroughout the laminate panel. In an exemplary case, a maximum of sixplies can be dropped at a specific depth location in the laminate stack.If a greater number of plies must be dropped, then these plies must beevenly distributed in groups of six or fewer plies throughout the depthof the laminate, as illustrates in FIG. 18. It will be appreciated thestep 113 advantageously can be implemented using any of the alternativesubroutines illustrated in FIGS. 9A∝13, which subroutines are alldiscussed in greater detail below.

Moreover, step 114 is subsequently performed to thereby extend the plyboundaries to establish needed ramps. As discussed above, the plyboundaries advantageously can be extended according to the subroutineset forth in FIGS. 14A through 14D, as discussed in greater detailbelow.

As a general rule, no more than one ply can terminate in a specificlocation in a basic laminate. By default, plies are extended prior totheir drop-off so that a ramp ratio of 20:1 advantageously can be formedin the primary load direction and a ramp ratio of 10:1 can be formed inthe transverse load direction. It will be appreciated that the primaryload direction is parallel to the zero degree axis as defined by thelocal finite element coordinate system, i.e., as defined by the finiteelement model. Preferably, the user can specify alternate ramp ratios,provided that the specified ramp ratio is not less than 3 degrees, normore than 90 degrees, in either or both directions.

It should be mentioned that extensions can be determined by starting inthe thickest region and working toward the thinnest region. Pliesextended in one region should continue in all adjacent regions alongapproximately collinear borders. Although this affects the start of theramp in some regions, this constraint ensures that smooth ramps will becreated between regions of different thicknesses. An example of panelsbefore and after carrying out extensions in adjacent regions can be seenin FIGS. 19 and 20, respectively. More specifically, the arrow #1 inFIG. 19 identifies a laminate region where ply extensions neglectingadjacent plies results in a laminate having numerous ramp comers and acomplex moldline geometry. In contrast, the arrow #1 in FIG. 20illustrates the point that modifying the onset of the ramp feature inadjacent regions of the laminate to account for plies terminating inthose adjacent regions results in a laminate having smooth ramp detailsand a simple inner moldline geometry.

Advantageously, the user can be given a choice of ply extension rules.The default rules will be used to create symmetric extensions. However,the user may choose to create non-symmetric extensions by modifying thedefault ply extension rules.

Symmetric extensions advantageously are created to minimize the area ofthe unsymmetrical region created by the transition. This is accomplishedby extending the plies in pairs, alternating above and below thecenterline of the laminate. Below the centerline, the plies closest tothe tool side are preferentially extended the furthest to simplifyplacement and alignment of the plies. Above the centerline, the pliesfurthest from the tool side are extended the furthest to stay symmetricwith its pair below the centerline. An example of symmetric extensionsis illustrated in FIG. 18. In FIG. 18, the arrow denoted #1 indicatesthat up to 6 plies can be dropped toward the centerline where minimalbending stress exists in the laminate; arrow #2 denotes a region whereinadditional plies are required to terminate at an alternate depth in thelaminate to avoid overloading adjacent plies; and arrow #3 illustratesthat the plies closest to the tool side extend furthest for increasedmanufacturability. In should also be noted that arrows #1 and #3illustrate that the plies are extended in symmetric pairs such thatsuccessive ply terminations alternate above and below the centerline ofthe laminate.

As an alternative, the user may wish to define extensions to simplifythe placement and alignment of plies during manufacturing. This isaccomplished by extending the plies closest to the tool side thefurthest in all cases. As a result, plies will not be dropped in pairs,thus creating a non-symmetric extension. An example of non-symmetricextensions may be seen in FIG. 21. More specifically, the arrow #1 inFIG. 21 illustrates a laminate transition region where the plies closestto the tool surface extend furthest above and below the centerline forimproved manufacturability, even though this results in unsymmetricterminations of ply pairs.

During step 115, the design is converted into a viewable form, e.g.,cross-sections, 3-D views, ply views, tables and/or reports to permitthe designer to visualize the design. A determination is then madeduring step 116 for whether the design is considered to be satisfactory.

In the event that the inquiry at step 116 produces a positive response,step 117 is performed to thereby return to the composites designoverview illustrated in FIG. 7. If the response is negative, thesubroutine makes a determination of whether or not the local laminatescan be redefined at step 118. If the answer is negative, a newconnectivity process is chosen (step 119) and step 113 repeats. If theanswer is affirmative, step 120 is performed to select critical regions.Furthermore, during step 121, an inquiry is performed to determine ifthe laminates in the critical regions are acceptable. When the answer isaffirmative, step 123 of the subroutine is performed to identify otherregions to modify; when the answer is negative, step 122 is performed tomodify critical laminate by a selected method. It will be noted that, asdiscussed above, the alternative methods which advantageously can beselected are illustrated in FIGS. 15A-15C and 16. FIGS. 15 and 16 willbe discussed in greater detail below.

During step 124, the regions are ordered by thickness, i.e., thickest tothinnest and during step 125, the bounds on modification, e.g., familyvariances, the number of adjacent plies, the number of adjacentterminations, and the number of continuous plies, are established. Then,the thickest region is compared to the next thickest region during step126. An inquiry is then performed as step 127 to determine whether athinner laminate can be obtained from a thicker laminate by theexpedient dropping of plies. When the answer is negative, step 128 isperformed to determine the number of plies dropped between the regionsand step 129 is performed to determine all combinations of availableplies to drop from the thickest region which sum equal to the totalnumber of plies to drop. In step 129, continuous plies are ignored. Atstep 130, an inquiry as to whether there are any ply drop combinationsavailable is made. When the answer is negative, step 131 is performed toreduce the total number of ply drops by 1 and step 129 is repeated.

In the event that the inquiry at step 130 is affirmative, step 132 isexecuted to calculate a new family for each of the ply dropcombinations, step 133 is performed to calculate the error in eachfamily member from the target and step 134 is initiated to select theply drop combination needed to minimize the average absolute error inthe family. Moreover, step 135 is performed to define the revised locallaminate for a thinner region. Following step 135, it is assumed thatthe thinner region is now the thickest region at step 136 and an inquiryis performed during step 137 to determine if there is another, thinnerregion. In the event that the answer is affirmative, step 126 isrepeated; if the answer is negative, step 113 is repeated to establishply connectivity.

It will be appreciated that many features may be included in theknowledge driven composite design optimization system to provide thelaminate designer with visual information regarding the present state ofthe laminate design. Although the primary focus of the paragraphsimmediately below is with respect to the visual presentation of data atthe end of steps 113 and 114 of FIGS. 8A and 8B, it will be appreciatedthat some percentage of the data is accessible by the laminate designerat every stage of the design process. For example, the original designsurface is immediately displayable upon selection of a surface, and anytime thereafter. Moreover, the original surface can be displayed as anyof a wireframe, a shaded surface, or a faceted surface. Rather thanattempt to discuss each visual display mode with respect to a singleassociated step, the general aspects of the user interface will now bedescribed.

The user advantageously can control knowledge driven composite designoptimization process, including PACKS, through a consistent graphicaluser interface (GUI). This GUI, in an exemplary case, can be createdusing OSF/Motif and standard Athena widgets. The GUI consists ofmultiple windows and dialog boxes for user input. Upon startup, alimited set of windows will appear. By default, these startup windowsconsistently appear in the same places on the screen for each session.An example of this default arrangement is illustrated in FIG. 22. Aspreviously discussed, the user can override this default through the useof X-window resources defined in the user's .Xdefaults file, whichpreferably is located, in an exemplary case, in the home directory ofthe user.

The main window of the GUI advantageously can display most of the viewsof the finite element model. This window appears upon startup fordisplay of the main menu. It should be mentioned that the menuadvantageously can be used to control all functionality common to theentire application, such as setting user preferences. The main window isdepicted in FIG. 22. Additionally, a message window appears uponstartup, to permit the display of status messages to the user, e.g.,when background activity will cause a delay in program initiation. Itwill be noted that these messages additionally provide the user withprogress information. The message window is also illustrated in FIG. 22.

It will be appreciated that, in addition to the main window, one or morechild windows pop up whenever the user selects an operation oroperations that the user desires to display along with the displaypresented in the main window. In particular, each of the followingoperations will pop up a new window:

(1) Cross Sections--When the user selects or creates a section cutlocation, a planform view window will pop up identifying the borders ofthe constant laminate regions and the cutting plane selected, asdepicted in FIG. 23. Moreover, when the user displays a created orselected cut, the cross section window will pop up, as depicted in FIG.24. This latter window advantageously can contain a menu with optionsthat apply only to cross sections, such as settings.

(2) Reports--Reports, either graphical or tabular, can be made to appearin a pop up window, as illustrated in FIGS. 25-29. These reports allowthe user access to design information in a multitude of formats. Forexample, FIG. 25 demonstrates a tabular report of region information andFIG. 26 illustrates a graphical representation of the number of plies inthe various regions. Summary ply data relating to overall component costcan be seen in the tabular report of FIG. 27. In addition, the systemadvantageously is capable of developing summary reports of the status ofthe analysis, as seen in FIGS. 28-29. These reports can include theinitial material properties and laminate definitions as well as thecurrent material properties and laminate definitions. Furthermore, thesereports summarize the total number of plies, the number of transitions,and the component weight for both the initial configuration and thecurrent configuration. It will be appreciated that these reports willfacilitate tradeoff studies for internal ply arrangement and willprovide an indication to the user of which solutions merit furtherconsideration, i.e., should be saved as new files for later recall andreuse.

(3) Loads--Internal element loads advantageously can be displayed in apop up child window as text or graphical reports, as depicted in FIG.30. The user can freely select a load condition and either the elementor region loads. Based on the user's selection, the load view will thenbe displayed in a new window.

(4) Dialog Boxes--Preferably, dialog boxes are used to obtain input fromthe user. During startup, dialog boxes for the main window, as well asthe draw and view dialogs will appear, as shown in FIG. 22. The drawdialog permits the user to specify what views of the model should bedisplayed and how they should appear when displayed. Other dialog boxesadvantageously can be used for user input during the laminate editingsteps. For example, the view dialog permits the user to manipulate thecurrent view. An interface to scrolling, panning, moving, zooming androtating views is provided for that purpose, as well as a view managerto allow the user to save the selected settings. Interactive dialogboxes allow the user to query for design information, or tointeractively modify the design. For example, FIG. 31 illustrates theresult of a border query to identify the ply connectivity at a specificborder. Similarly, FIG. 32 depicts the result of an interactive regionedit, allowing the user access to local ply and material properties. Inaddition, user input to laminate transitions editing advantageously canbe performed through the laminate transitions dialog, which is depictedin FIGS. 28 and 29. Moreover, editing laminate transitions may pop upother dialog boxes permitting editing of target families, to invoke theinterface of the laminate designer subroutine, as illustrated in FIG.33, or to edit ply or region data. The ply solutions, including theconnectivity between regions and the extensions necessary to produce theramps, can be visualized as seen in FIGS. 34 and 35. In addition, toallow the user the extra functionality necessary to drawthree-dimensional plies, a three-dimensional ply's dialog box, depictedin FIGS. 36 and 37, can be used. Additional dialog boxes advantageouslycan be used to facilitate the laminate design process. For example, aselect loads dialog box allows the user to select which loads to are tobe applied.

(5) Views--A number of distinctive views are provided by the knowledgedriven composite design optimization system and corresponding process toassist the user in visualizing the part or panel both during the designprocess or after the design is finalized. It will be appreciated thatthe latter views assist the design team in communicating with thefabrication facility to ensure that all aspects of the design arereflected in the finished panel. For example, the finite element modelmesh can be displayed immediately upon selection of a surface. Asmentioned previously, the FEA mesh may be displayed as a wireframe, ashaded surface, or a faceted surface. In addition, an identical laminateregions view allows the design team to determine areas of identicallaminate stacks. It will be appreciated that the identical laminateregions view requires that the regions must be generated before they canbe displayed. The regions are created by joining adjacent elements inthe FEA mesh which have an identical laminate definition. The regionboundaries define where transitions will occur in the laminate. Theseregions may also be displayed as a wireframe, a shaded surface, or afaceted surface. Furthermore, an unextended plies view can be used toshow a projection of each ply onto evenly spaced copies of the designsurface, assuming each ply termination will be on a region boundary.Moreover, all views must also be capable of being printed to auser-selected scale, saved for future printing, or exported toUNIGRAPHICS (TM) as IGES entities.

(6) Text Output--Various specialized textual presentations can also beprovided by the composite design optimization system to enhanceunderstanding of both the composite design optimization process and thecompleted laminate design. For example, tabular views of the laminateply data can be generated by the knowledge driven composite designoptimization system for display and printing, as depicted in FIG. 27. Inan exemplary case, this data advantageously can include ply detail dashnumber, ply sequence number, fiber orientation, material stock number,material density, cured ply thickness, ply area, ply perimeter, plymaximum length and width, and the defining ply boundary. In addition,laminate tables are displayable in either a cross section view orthrough a region query. A laminate table contains the ply number(sequence number), ply detail dash number, fiber orientation, andmaterial stock number for the laminate of a given region. Moreover, amaster ply table contains the ply number (sequence number), ply detaildash number, fiber orientation, and material stock number for every plyin the component.

It will be noted that each layer within a given laminate is assigned aply detail dash number and a ply number or sequence number, whichindicates the sequence of lamination of each ply detail, starting with 1as the first ply laid down on the tool surface and increasingsequentially as the laminate is assembled. By convention, all plydetails to be applied in the same sequence, i.e., set, have the samesequence number. All plies within a given lay-up having the exact sameplanform fiber orientation and material composition are permitted toshare a common dash number providing they fall in different ply levelswhile identical ply details falling on the same ply level are assigneddifferent dash numbers.

It should also be mentioned that for each view and table, the user canperform zooming in and out, scrolling up and down, panning left andright, and rotation around the X, Y and Z axis of the display screen ofthe computer system running the composite design optimization processsoftware. The user advantageously can save any view by a selected name,and then recall that view by selecting it from a list of saved views.These actions are accessible at any time, i.e., they may be performedduring intermediate steps in the operation. In this manner, a user couldquery a feature, zoom in to select one parameter, pan to select another,and then generate new results based on the indicated design changes.

Preferably, a laminate visualization overview function is provided withthe system, the primary purpose of which is to allow the user to browsethrough several different three-dimensional views of the laminate. Theseviews allow, for example, the laminate designing user to get a quickoverview of the laminate and get an idea of the quality of its design ascompared with other possible designs based upon the experience of theuser. In addition, this overview function also allows laminatemanufacturing users to interactively select the views of the laminate,its plies, or its cross sections that they find will best allow them toconceptualize the laminate. Preferably, the user can interactivelyannotate any view with rosettes and end of ply markers. Rosettesadvantageously allow the designer to specify the spot where theprescribed orientation is applied to the mold, e.g., during lay-up. Inan exemplary case, the designer can locate the rosette anywhere withinthe outline of the part. Furthermore, the end of ply markers allow thedesigner to completely define the ply outline. The end of ply markersadvantageously can be created with a leader line pointing toward the plyinterior. In addition, all cross section views can be annotated with oneor more laminate tables.

It should again be mentioned that the alternative subroutinesillustrated in FIGS. 9A-13 correspond to step 113 in FIGS. 8A and 8B.Each of these alternative embodiments will now be discussed in greaterdetail immediately below.

The subroutine of FIGS. 9A and 9B, which advantageously illustrates themethod whereby ply connectivity is established according to theso-called dropping plies out-to-in method starts with the step 201 inwhich a query is conducted for every region to determine the number ofplies in each region. Then, step 202 is performed to determine whetherany of the regions have an odd number of plies. In the event that theanswer is affirmative, step 203 is performed to establish one continuouscenterline ply; when the answer is negative, step 204 is performed toestablish two continuous centerline plies. Step 205 is then performed toquery every region to determine the maximum number of continuous surfaceplies. During step 206, the connectivity of continuous surface pliespreferably is established after which step 207 is performed to queryevery region for additional continuous centerline plies. At step 208, adetermination is made for whether there are additional potentialcontinuous centerline plies. If the answer is affirmative, step 209 isinitiated to establish the connectivity of continuous centerline plies,subject to limits on the maximum number of adjacent terminations andplies and step 210 is executed to establish the order in which to accessthe borders, e.g., thickest to thinnest, thinnest to next thickest,thinnest to thickest, greatest number of terminations to fewest numberof termination, and fewest number of terminations to greatest number ofterminations, according to geometric position. Step 211 is thenperformed in order to establish the order for moving through theregions, e.g., thickest to next thickest, thickest to thinnest, thinnestto next thickest, thinnest to thickest, again according to geometricposition. Then, step 212 is performed to establish the starting regionand step 213 is performed to establish the initial border to beconsidered. It will be noted that when the answer to the question posedin step 208 is negative, step 209 is skipped, i.e., the subroutine jumpsto step 210.

Following the prefatory steps discussed immediately above, step 214 isperformed to determine whether the outermost unassigned plies on oneside of the centerline advantageously can be connected. If the answer isnegative, step 215 is executed to connect the outermost unassigned plyin a thinner region to the outermost similar ply in the thickest regionand to designate the plies outward of this connection as dropping. Incontrast, when the answer is affirmative, step 216 is performed toconnect the outermost unassigned plies, thus assigning these plies. Inany event, step 217 is then performed to determine whether the outermostunassigned ply on the other side of the centerline advantageously can beconnected. An affirmative reply permits step 218 to be performed tothereby connect the outermost unassigned plies on the other side of thecenterline, thus assigning these plies also. On the other hand, anegative response at step 217 initiates step 219 to connect theoutermost unassigned ply in a thinner region to the outermost similarply in the thickest region and to designate plies outward of thisconnection as dropping.

A determination is then made for whether there are any more plies towardthe centerline at step 220. An affirmative answer causes step 214 to berepeated; a negative answer initiates step 221, which determines whetherthere is another border to investigate in this region. If the answer isaffirmative, step 214 is repeated after step 222 is performed toestablish the border to be evaluated based on the previously establishedorder. When the response to step 221 is negative, step 223 is performedto determine whether there are more regions to investigate. Step 224,which calculates the boundary of every ply, and step 225, which returnsto the PACKS Process of FIGS. 8A and 8B are performed when the answer isnegative. When the answer is positive, step 226 is first performed toestablish the next region to investigate based on the previouslyestablished order and then step 213 is repeated.

An alternative preferred embodiment of the composite design optimizationprocess according to the present invention illustrated in the flowchartof FIGS. 10A and 10B will now be described briefly. It should bementioned that the subroutine depicted in FIGS. 10A and 10B refers tothe so-called method of establishing ply connectivity by dropping pliesat seed plies moving out-to-in. It should also be mentioned that thepreparatory steps, i.e., steps 301 to 313 of FIGS. 10A and 10B arevirtually identical to similar steps in the flowchart of FIGS. 9A and9B. Thus, steps 301 to 313 of FIGS. 10A and 10B will not be described inthe interest of brevity.

Jumping ahead to step 314, the total number of plies to drop at theborder is determined. Then, step 315 is performed to divide the totalnumber of dropped plies by two, and then by the number of adjacentterminations; based on these results, the next highest integer number isdetermined. Next, step 316 is executed to divide the number ofunassigned plies in a thicker laminate by two, then by the integer justcalculated in step 315. The result is then truncated to an integer (n).During step 317, a "seed" termination is established every Nth ply,counting up from the continuous centerline ply, on the thicker laminate.

A series of queries is then performed to determine ply optimization withrespect to the seed ply. First, step 318 is performed to determine ifthe outermost ply on one side of the centerline is the seed ply. Whenthe answer is negative, an additional query is performed at step 319 todetermine whether the outermost unassigned plies on one side of thecenterline can be made continuous. If the answer is affirmative, step320 is performed to connect the outermost unassigned plies, thus makingthese plies assigned; when the answer is negative, step 321 is executedto connect the outermost unassigned plies in the thinner region to theoutermost similar ply in the thickest region and to assign plies outwardof the connection as dropping. It will be noted from FIGS. 10A and 10Bthat when the response at step 318 is affirmative, step 332 is performedto connect the outermost unassigned plies in the thinner region to theoutermost similar ply which is not the outermost ply in the thickestregion and to assign the plies outward of the connection as dropping. Inany event, step 322 is performed following completion of one of thesteps 320, 321 and 332.

At step 322, another query is performed in order to determine whetherthe outermost ply on the other side of the centerline is a seed ply.Assuming the answer is YES, step 323 is performed to connect theoutermost unassigned plies in the thinner region to the outermostsimilar ply which is not the outermost ply in the thickest region and toassign the plies outward of the connection as dropping. In the eventthat the answer is negative, step 324 can be performed to determinewhether the outermost unassigned plies on the other side of thecenterline advantageously can be made continuous. When the answer isaffirmative, step 325 is executed to connect the outermost unassignedplies, thus making these plies assigned; when the answer is negative,step 326 is performed to connect the outermost unassigned plies in thethinner region to the outermost similar ply in the thickest region andto assign the plies outward of the connection as dropping.

Regardless of the action taken responsive to step 322, step 327 is thenperformed to determine whether there are more plies toward thecenterline. When the answer is affirmative, the subroutine repeats step318 and subsequent steps; when the answer is negative, step 328 isperformed to determine whether there is another border to investigate inthis region. If there are no more borders, step 329 is performed todetermine whether there is another region to investigate. When theanswer at step 328 is affirmative, the subroutine jumps to the start ofstep 313; when the answer at step 329 is affirmative, the subroutinejumps to the start of step 312. In the event that the answer at bothsteps 328 and 329 are negative, step 330 is performed to calculate theboundary of every ply and then step 331 is performed to return to thePacks Process of FIGS. 8A and 8B.

Another alternative preferred embodiment of the composite designoptimization process according to the present invention illustrated inthe flowchart of FIGS. 11A and 11B will also be described briefly. Itshould be noted FIGS. 11A and 11B refer to the so-called method ofestablishing ply connectivity by dropping Ply Packs at seed plies movingout-to-in. It should also be mentioned that the preparatory steps, i.e.,steps 401 to 413 of FIGS. 11A and 11B are virtually identical to similarsteps in the flowcharts of FIGS. 9A-9B and 10A-10B. For that reason, adetailed discussion regarding steps 401 to 413 of FIGS. 11A and 11B willnot be provided.

Starting with step 414, the total number of plies to drop at the borderis first determined. Then, step 415 is performed to divide the totalnumber of dropped plies by two, and then by the number of adjacentterminations; based on these results, the next highest integer number isdetermined. Next, step 416 is executed to divide the number ofunassigned plies in a thicker laminate by two, then by the integer justcalculated in step 415. The result is then truncated to an integer (n).During step 417, a "seed" termination is established every Nth ply,counting up from the continuous centerline ply, on the thicker laminate.

Step 418 is then performed to determine whether the outermost ply on oneside of the centerline is within one ply of a seed ply. If the answer isnegative, step 419 is performed to question whether the outermostunassigned plies on one side of the centerline advantageously can bemade continuous; when the answer is affirmative, step 432 is executed tosearch for a viable pattern of fewer than the limit for the number ofadjacent terminations to drop, to then connect the unassigned pliesaccording to the search results, and to assign plies outward of theconnection as dropping. With respect to step 419, when the answer isaffirmative, step 420 is executed to connect the outermost unassignedplies, thus making these plies assigned; when the answer is negative,step 421 is performed to connect the outermost unassigned plies in thethinner region to the outermost similar ply in the thickest region andto assign the plies outward of the connection as dropping. In any event,step 422 is performed following completion of one of the steps 420, 421and 432.

At step 422, another query is performed in order to determine whetherthe outermost ply on the other side of the centerline is within one plyof a seed ply. Assuming the answer is YES, step 423 is then performed tosearch for a viable pattern of fewer than the limit for the number ofadjacent terminations to drop, to connect unassigned plies according tothe search results, and to assign plies outward of the connection asdropping. In the event that the answer is negative, step 424 can beperformed to determine whether the outermost unassigned plies on otherside of the centerline advantageously can be made continuous. When theanswer is affirmative, step 425 is executed to connect the outermostunassigned plies, thus making these plies assigned; when the answer isnegative, step 426 is performed to connect the outermost unassignedplies in the thinner region to the outermost similar ply in the thickestregion and to assign the plies outward of the connection as dropping.

Irrespective of the action taken responsive to step 422, step 427 isthen performed to determine whether there are more plies toward thecenterline. When the answer is affirmative, the subroutine repeats step418 and subsequent steps; when the answer is negative, step 428 isperformed to determine whether there is another border to investigate inthis region. If there are no more borders, step 429 is performed todetermine whether there is another region to investigate. When theanswer at step 428 is affirmative, the subroutine jumps to the start ofstep 413; when the answer at step 429 is affirmative, the subroutinejumps to the start of step 412. In the event that the answer at bothsteps 428 and 429 is negative, step 430 is performed to calculate theboundary of every ply and then step 431 is performed to return to thePACKS Process of FIGS. 8A and 8B.

Yet another alternative preferred embodiment of the composite designoptimization process according to the present invention illustrated inthe flowchart of FIGS. 12A and 12B will also be described briefly. Itshould be noted that the connectivity subroutine depicted in FIGS. 12Aand 12B refers to the so-called method of establishing ply connectivityby dropping ply packs at seed plies moving in-to-out. It should also bementioned that the prefatory steps, i.e., steps 501 to 516 of FIGS. 12Aand 12B are substantially similar to like numbered steps in theflowcharts of FIGS. 9A-9B through 11A-11B. For that reason, a detaileddiscussion regarding steps 501 to 516 of FIGS. 12A and 12B will beomitted.

Starting with step 517, a "seed" termination is established at theinnermost unassigned ply and every Nth ply thereafter, counting up fromthe centerline plies, on the thicker laminate. Step 518 is thenperformed to determine whether the innermost ply on one side of thecenterline is within one ply of a seed ply. If the answer is negative,step 519 is performed to question whether the innermost unassigned plieson one side of the centerline advantageously can be made continuous;when the answer is affirmative, step 532 is executed to search for aviable pattern of fewer than the limit for the number of adjacentterminations to drop from the thicker region, and to then disconnect andreconnect the unassigned plies according to the search results. Withrespect to step 519, when the answer is affirmative, step 520 isexecuted to connect the innermost unassigned plies, thus making theseplies assigned; when the answer is negative, step 521 is performed toconnect the innermost unassigned plies in the thinner region to theinnermost similar ply in the thickest region and to assign the pliesinward of the connection as dropping. In any event, step 522 isperformed following completion of one of the steps 520, 521 and 532.

At step 522, another query is performed in order to determine whetherthe innermost ply on the other side of the centerline is within one plyof a seed ply. Assuming the answer is YES, step 523 is then performed tosearch for a viable pattern of fewer than the limit for the number ofadjacent terminations to drop from the thicker region, and to disconnectand reconnect unassigned plies according to the search results. In theevent that the answer is negative, step 524 can be performed todetermine whether the innermost plies on other side of the centerlineadvantageously can be made continuous. When the answer is affirmative,step 525 is executed to connect the innermost unassigned plies, thusmaking these plies assigned; when the answer is negative, step 526 isperformed to connect the innermost unassigned plies in the thinnerregion to the innermost similar ply in the thickest region and to assignthe plies inward of the connection as dropping.

Irrespective of the action taken responsive to step 522, step 527 isthen performed to determine whether there are more plies toward themoldline. When the answer is affirmative, the subroutine repeats step518 and subsequent steps; when the answer is negative, step 528 isperformed to determine whether there is another border to investigate inthis region. If there are no more borders, step 529 is performed todetermine whether there is another region to investigate. When theanswer at step 528 is affirmative, the subroutine jumps to the start ofstep 513; when the answer at step 529 is affirmative, the subroutinejumps to the start of step 512. In the event that the answers at bothsteps 528 and 529 are negative, step 530 is performed to calculate theboundary of every ply and then step 531 is performed to return to thePACKS process of FIGS. 8A and 8B.

A fifth alternative preferred embodiment of the knowledge drivencomposite design optimization process according to the present inventionillustrated in the flowchart of FIG. 13 will now be described briefly.However, it should first be noted that the subroutine depicted in FIG.13 refers to the so-called method of establishing ply connectivity bythe ply growth method. It should also be noted that the prefatory steps,i.e., steps 601 to 610 of FIG. 13 are substantially similar to likenumbered steps in the flowcharts of FIGS. 9A through 12B. Therefore, adetailed discussion regarding steps 601 to 610 of FIG. 13 will beomitted. It will be mentioned that the steps associated with FIG. 13 arenot continuously numbered; numbers are selected to correspond to likesteps in FIGS. 9A through 12B.

Starting with step 611a, the order for moving through the regions, e.g.,thickest to next thickest, thickest to thinnest, thinnest to nextthickest, or thinnest to thickest, according to geometric position, isestablished. Then, step 611b is performed to establish the order formoving through the plies, e.g., outer to inner in the key region, innerto outer in the key region, by geometry, and step 611c is performed toestablish the ply to investigate. Afterwards, step 612 is executed toestablish the region to investigate and step 613 is performed toestablish the border to investigate.

Step 619 advantageously can be performed to question whether theoutermost unassigned plies on one side of the centerline advantageouslycan be connected; when the answer is affirmative, step 620 is executedto connect the outermost unassigned plies, thus making these pliesassigned. Irrespective of the answer at step 619, step 628 is thenperformed to determine whether there is another border to investigate inthis region. If there are no more borders, step 629a is performed todetermine whether there is another region to investigate for this ply.When the answer at step 628 is affirmative, the subroutine jumps to thestart of step 613; when the answer at step 629a is affirmative, thesubroutine jumps to the start of step 612. In the event that the answerat both steps 628 and 629a is negative, step 629b is then performed todetermine whether there is another ply to evaluate. When the answer isaffirmative, the subroutine loops back to the start of step 611c; whenthe answer is negative, step 630 is performed to calculate the boundaryof every ply and then step 631 is performed to return to the PACKSprocess of FIGS. 8A and 8B.

As discussed previously with respect to step 114 in FIGS. 8A and 8B,ramps are an integral feature of every ply and thus are preferablycalculated with the base laminate. Ramps are produced to preclude thetermination of more than one ply at a specific location. Thus, the pliesare extended slightly such that the ply terminations advantageously forma gradually sloping thickness transition. In order to design to the plylevel, it must be established which ply boundaries should be extended tocreate the necessary ramps. The process for defining these extendedboundaries is detailed in FIGS. 14A through 14D. It should be mentionedthat the process depicted in these figures embodies alternate methodsfor extending plies, depending on the requirements and geometry of thecomponent. Again, the innovation lies in the systematic and well-definedapproach which ensures a consistent and trackable extension methodology.It should also be mentioned that the discussion below addresses FIGS.14A through 14D collectively.

The subroutine corresponding to step 114 of FIGS. 8A and 8B starts withstep 701, in which the boundary of every ply, assuming a terminationexists at the borders, is defined. Step 702 is then performed toestablish the order for evaluating the borders, e.g., thickest region tothinnest, or vice versa, or the border with the greatest or the fewestnumber of terminations. Afterward, step 703 is executed to establish theborder to examine. During step 704 a determination is made as to whetherthere is more than one ply terminating at the border. When the answer isnegative, an additional inquiry is made at step 705 to determine whetherthere is another border to examine. When the answer is negative, step706 is performed to calculate the extended ply boundaries for every plyand then step 707 is performed to return to the PACKS process of FIGS.8A and 8B. In contrast, when the answer is affirmative, the subroutineloops back to the beginning of step 703. It will be noted that when theanswer to the inquiry of step 704 is positive, steps 708 and 709 areperformed.

During step 708, the number of plies terminating at the border isdetermined. Then, during step 709, the predominant orientation of theborder geometry with respect to a predetermined material axis isdetermined. Step 710 is then performed to determine whether the defaultramp ratio is acceptable. If the answer is affirmative, step 711 isperformed to determine whether the border is oriented within 45° of theX-axis. It will be noted that the answers in steps 710 and 711 are usedto establish the default ramp ratio. More specifically, if the answer isnegative at step 710, step 715 is performed to define ramp ratio asdesired, i.e., 3<θ<90. When the answer is negative to the inquiry ofstep 711, step 712 is used to define a default ramp ratio of 20:1; whenthe answer is affirmative, step 713 defines the default ramp ratio asbeing 10:1.

Irrespective of the answers to the inquiries in steps 710 and 711, step714 is then performed to determine whether this border is collinear withanother border, i.e., within 0.5 inches and/or 5°. When the answer isnegative, step 716 is performed to determine whether symmetricextensions are desired. When the answer is affirmative, step 717 is thenperformed to establish the starting ply as the second closesttermination to the centerline on tool side; when the answer is negative,the subroutine jumps to step 737, which is discussed in greater detailbelow.

Execution of step 717 is followed by execution of step 718, in which theply from the previous terminating ply is extended at twice the rampratio. An inquiry is then made at step 719 in order to determine ifthere are more terminating plies below the centerline. When the answeris affirmative, step 720 is performed to establish the next terminationfrom the centerline towards the tool surface as the starting ply andthen step 718 is repeated. When the answer is negative, step 721 isexecuted to establish the starting ply as the second closest terminationto the centerline away from the tool side. Step 722 is then performed toextend the ply from the previous terminating ply at twice the rampratio. Another inquiry is then made at step 723 in order to determinewhether there are more plies terminating above the centerline. When theanswer is affirmative, step 724 is performed to establish the nexttermination from the centerline away from the tool surface as thestarting ply and then step 722 is repeated; when the answer is negative,the subroutine jumps to the start of step 705.

Assuming the answer is affirmative to the inquiry of step 714, step 725is performed to determine whether the plies have been extended in acollinear border. When the answer is negative, step 716 is performed;when the answer is affirmative, step 726 is executed to extend the sameplies similarly in this border, i.e., disregarding the local border.Another inquiry is then performed at step 727 to determine if there areadditional terminating plies. When the answer is negative, thesubroutine jumps to the start of step 705; when the answer isaffirmative, step 728 is performed to determine whether symmetricextensions are desired. In the event that such extensions are notdesired, the subroutine jumps to the beginning of step 749, which stepwill be discussed further below; when the answer is affirmative, step729 is executed to set the starting ply as the closest unextendedtermination to the centerline on the tool side and then step 730 isperformed to extend the ply from the previous longest extended ply belowthe centerline at twice the ramp ratio.

Following step 730, an inquiry is made at step 731 to determine whetherthere are more terminating plies below the centerline. When the answeris affirmative, step 732 is executed to establish the next terminationfrom the centerline towards the tool surface as the starting point andthen step 730 is repeated. When the answer is negative, step 733 isperformed to set the starting ply as the ply closest to the unextendedtermination to the centerline away from the tool side. Step 734 is thenperformed to extend the ply from the previously longest extended plyabove the centerline at twice the ramp ratio. An inquiry is then made atstep 735 to determine whether there are more plies terminating above thecenterline. When the answer is affirmative, step 736 is used toestablish the next termination from the centerline away from the toolsurface as the starting ply and step 734 is repeated; when the answer isnegative, the subroutine jumps to the start of step 705.

As discussed above, when the answer is negative at step 716, step 737 isperformed to determine if there are any continuous centerline plies.When the answer is affirmative, step 738 is performed to establish thestarting ply as the second closest termination to the centerline on thetool side and then step 739 is performed to extend the ply from theprevious terminating ply at twice the ramp ratio. Another inquiry isthen made at step 740 to determine if there are more terminating pliesbelow the centerline. When the answer is affirmative, step 741 is usedto set the next termination from the centerline towards the tool surfaceas the starting ply and step 739 is repeated; when the answer isnegative, step 742a is performed to establish the starting ply as thesecond furthest termination from the tool side and step 742b isperformed to extend the ply from the previous terminating ply at twicethe ramp ratio. Then step 743 is performed to determine whether thereare more plies terminating above the centerline. When the answer isaffirmative, step 744 is used to set the next termination from thecenterline away from the tool surface as the starting ply and step 742bis repeated; when the answer is negative, the subroutine jumps to thestart of step 705.

When the answer is negative to the inquiry at step 737, step 745 isperformed to establish the starting ply as the second furthesttermination from the tool side and then step 746 is used to extend theply from the previous terminating ply at the ramp ratio. During step747, an inquiry is made as to whether there are more terminating plies.If the answer is affirmative, step 748 is performed to establish thenext termination towards the tool surface as the starting ply and step746 is repeated; when the answer is negative, the subroutine jumps tothe start of step 705.

In addition, when the answer to the inquiry at step 728 is negative,step 749 is performed to determine whether there are any continuouscenterline plies. Then step 750 is performed to establish the startingply as the closest unextended termination to the centerline on the toolside while step 751 is used to extend the ply from the previous furthestextension at twice the ramp ratio. During step 752, a determination ismade for whether there are more terminating plies below the centerline.When the answer is affirmative, step 753 is performed to establish thenext termination from the centerline towards the tool surface as thestarting ply and then step 751 is repeated. When the answer is negative,step 754 is used to establish the starting ply as the furthestunextended termination from the tool side, and step 755 is performed toextend the ply from the previous furthest extension according at twicethe ramp ratio. Step 756 is the performed to determine if there are anymore plies terminating above the centerline. When the answer isaffirmative, step 757 is executed to establish the next terminationtoward the centerline as the starting ply; when the answer is negative,the subroutine jumps to the start of step 705.

When the answer to the inquiry made at step 749 is negative, step 758 isperformed to establish the starting ply as the furthest unextendedtermination from the tool side and step 759 is used to extend the plyfrom the previous extension at the ramp ratio. Step 760 is thenperformed to determine whether there are more terminating plies. Whenthe answer is affirmative, step 761 is performed to establish the nexttermination towards the tool surface as the starting ply and step 759 isrepeated; when the answer is negative, the subroutine jumps to the startof step 705.

It will be recalled that only a brief explanation regarding theavailable alternatives with respect to step 122 of FIGS. 8A and 8B waspresented above. A more detailed discussion of the alternativeembodiments will now be presented while referring to FIGS. 15 and 16.

When it is determined that the laminates in critical regions are notacceptable as determined in step 121 of FIGS. 8A and 8B, a so-calledlaminate designer subroutine according to the present inventionadvantageously can be performed. The primary purpose of the laminatedesigner subroutine is to reduce the manual work of the design andanalysis team by automating the computation and documentation of localply stacking sequence in a given region. The laminate designersubroutine advantageously is capable of accurately and repeatedlydetermining the most effective local laminate definition for a criticalregion, and providing this input to the transition routine to ensure auniform ply connectivity throughout the part which results in the fewesttransitions and the largest continuous plies. It will be appreciatedthat the laminate designer subroutine makes extensive use of rules andbest practices reflecting design, analysis, cost and manufacturingconstraints.

The laminate designer subroutine starts with step 801, in which userinputs including: name of saved output file; laminate thickness; maximumallowed thickness; ply thickness; number of materials; materialproperties, i.e., stiffness, Poisson's ratio, thermal expansioncoefficients, stress and strain allowables; laminate family; allowedvariation in family; extreme bounds on family; number of similaradjacent plies allowed; surface cloth material desired for mold linepanels; loading options; failure criteria, e.g., maximum stress, maximumstrain, Tsai-Hill, bearing-bypass, etc.; number of load cases; loadangle with respect to material axis; in-plane loads and moments;pressure on the panel; panel geometry; data reduction flags, i.e., thenumber of desired solutions based on the strength or stiffnessrequirements (for strength the most positive safety margin, the leastpositive safety margin and a defined number of intermediate solutions,for stiffness, the most and least stiff and a defined number ofintermediate solutions for each primary stiffness) are established.Then, step 802 is performed to vary the percentage of 0° plies.

A determination is then made at step 803 for whether the percentage of0° plies is greater than a predetermined minimum percentage. When theanswer is affirmative, step 804 is performed to determine whether thereare at least two 0° plies. When the answer is negative at steps 803 and804, step 802 is repeated; when the answer is affirmative at step 804,step 805 is executed to vary the percentage of 45° plies. Afterwards,step 806 is performed to determine whether the percentage of 45° degreeplies is greater than a predetermined minimum percentage. If the answeris affirmative, step 807 determines whether there are at least two 45°plies in the stack. When the answer is negative at both steps 806 and807, step 805 is repeated; when the answer is affirmative at step 807,step 808 is applied to vary the percentage of 90° plies. Then, step 809is performed to verify that the percentage of 90° plies is greater thana predetermined minimum percentage. It the answer is affirmative, step810 is performed to determine whether the summation of percentage of 0°plies, percentage of 45° plies and percentage of 90° plies is equal to100 percent. If the answer is negative at either step 809 or 810, step808 is repeated. However, when the answer is affirmative at step 810,step 811 is performed to initialize the thickness, and the number andtypes of plies.

Following step 811, step 812 is performed to determine whether thecurrent panel is a moldline panel. When the answer is affirmative, step813 is performed to determine whether the surface material is cloth;when the answer is negative, the laminate designer subroutine jumps tostep 814. If the answer is affirmative at step 813, step 814 isinitiated to determine whether the thickness is greater than the maximumallowed thickness; otherwise, step 811 is repeated.

When the answer is affirmative at step 814, step 805 is repeated.However, when the answer is negative, step 815 is executed to determinewhether there is an integer number of 0° plies. When the answer isaffirmative, step 816 is performed to determine whether there is an eveninteger number of 45° plies. When the answer is affirmative, step 817 isperformed to determine if there is an integer number of 90° plies. Whenthe answer is affirmative, step 818 is performed to determine if thereis an odd number of 0° plies, and if there is an odd number of 90°plies. When the answer is negative, step 819 is performed to incrementthe thickness by one ply thickness. It will be noted that when theanswer is negative in any of steps 815, 816 or 817, step 819 is alsoperformed. Then, step 814 is repeated.

In response to the inquiry made at step 818, when the answer isaffirmative, step 820 is performed to adjust angle of layer 1, step 821is executed to reduce the number of available plies of the type used,and then step 822 is used to adjust the angle of layer N. An inquiry isthen made at step 823 to determine whether the angle corresponds to anavailable ply. When the answer is affirmative, step 824 is performed todetermine whether the +45° and -45° plies are adjacent to one another;when the answer is negative, step 822 is repeated. In the event that theanswer is affirmative at step 824, step 825 is performed to determinewhether there are too many like plies adjacent to one another; when theanswer is negative, step 822 is repeated. When the response at step 825is YES, step 822 is repeated; when the answer is NO, step 826 isperformed to reduce the number of available plies of the type used.

A check is then performed at step 827 to determine whether the ply beingconsidered is the centerline ply. A negative response causes performanceof step 828, which increments the ply ID by one, i.e., n=n+1, and thenstep 822 is repeated. When the answer is affirmative, step 829 isexecuted to determine whether there are too many similar plies adjacentto one another at the centerline. When the answer is affirmative, step822 is repeated; when the answer is negative, step 830 is initiated toperform classical lamination theory adjustments and to calculate theterms of an ABD matrix. Then, step 831 is executed to perform astability analysis for moments due to bending or buckling, step 832 isperformed to add the thermal loads to the mechanical loads, step 833 isperformed to calculate ply stresses, strains, and safety factors, andstep 834 is performed to find the minimum safety factor. In connectionwith step 834, it should be mentioned that the transverse ply is ignoredif less than 25 percent of the plies are affected.

Next, step 835 is performed to determine whether the minimum safetyfactor is less than 1.0 for the current stacking sequence. When theanswer is negative, step 836 is performed to either print the solution,or store the solution for ensuing reduced solution set operations; whenthe answer is affirmative, step 837 is performed to determine whetherthis is the last possible ply stacking sequence. If the answer isaffirmative, step 838 is performed to determine whether the minimumsafety factor was greater than or equal to 1.0 for any of the stackingsequences evaluated. Responsive to this inquiry, step 839 is performedto determine whether there are additional families to investigate withthis percentage of 0° plies when the answer is affirmative. When theanswer is negative, step 840 is initiated to increment the thickness tothe minimum required to achieve a positive safety margin, i.e., ifstrength is the critical ratio, the stacking sequence is increased bythe maximum safety factor, if buckling is the critical ratio, the stackis increased by one ply. Then, step 814 is repeated. In contrast, whenthe answer at step 839 is negative, step 841 is executed to determinewhether there are any additional families to investigate. If the answeris negative, step 842 is performed to reduce the solution set based uponthe input parameters and then step 843 is performed to return to PACKS.In the event that the answer is affirmative at step 839, the laminatedesigner subroutine jumps to step 805; when the answer is affirmative atstep 841, the laminate designer subroutine jumps to step 802.

It will be noted that in the event that the answer at step 837 isnegative, step 844 is performed to return to adjusting orientation ofthe Nth layer until all of the successive sequences have beeninvestigated, starting with the ply closest to the centerline andworking to the first layer. When no further stacking sequences remainfor the current family, the laminate designer subroutine jumps to thestart of step 838.

As previously discussed, the laminate designer subroutine advantageouslyreduces the manual work of the design and analysis team by automatingthe computation and documentation of local ply stacking sequence in agiven region. Preferably, the laminate designer subroutine is capable ofaccurately and repeatedly determining the most effective local laminatedefinition for a critical region, and providing this input to thetransition subroutine to ensure a uniform ply connectivity throughoutthe part which results in the fewest transitions and the largestcontinuous plies. It will be appreciated that the laminate designersubroutine makes extensive use of rules and best practices reflectingdesign, analysis, cost and manufacturing constraints. It will also beappreciated that the knowledge based design process permits the user,after building a laminate in 3-D model space, to add or remove pliesfrom the laminate. When secondary structural features are to beincorporated into the model, the user advantageously can refine themodel further to meet new laminate requirements.

In order to determine an optimum laminate solution, further possiblelay-ups can be generated using the laminate designer subroutine, whichsubroutine, given a number of input criteria, generates starting andending stacking sequences for use with the laminate transition editing.Overall weight of the solutions advantageously can be compared to designcriteria to determine the optimum laminate continuity solution whichmeets the user's needs. Preferably, these outputs are accessible to theuser as both tabular and graphical reports. Moreover, the user ispermitted to select a solution to incorporate into the laminate.

Inputs to the laminate transition subroutine include the thickness ofthe selected region, the maximum thickness to which it can be increased,the target laminate family, the variation allowed in the laminatefamily, and the absolute maximum and minimum percentages of any plyorientation. Furthermore, the user advantageously can be allowed to setlimits on the number of adjacent plies of identical orientation whichare allowed both within the laminate and at the centerline, the numberof adjacent ply terminations to allow, and the materials desired forconstruction of the laminate.

The user preferably is allowed to specify options for reducing thenumber of solutions from the laminate designer subroutine based uponeither stiffness or strength criteria. For stiffness solutions, therequired inputs are a number of target solutions for each term in thebending stiffness matrix, and the number of terms to save near eachtarget. For strength solutions, the required inputs are the failurecriteria, i.e., maximum strain, maximum stress, Tsai-Hill, andbearing-bypass, the definition of the load cases, and the desired numberof solutions. Furthermore, routines advantageously can be developed fordetermining average geometry and loads within regions bounded bysubstructure, for basic stability estimations.

In an exemplary case, the output of the laminate designer subroutineincludes the requested number of stacking sequences for the region, themechanical properties of the laminates, an ABD matrix and effectivehomogeneous properties, and the minimum margin of safety, if strengthsolutions are to be performed. The system is capable of using eachoutput to generate intermediate laminates, and comparing the overallweight of the solutions to determine the optimum least weight laminatecontinuity solution. These outputs preferably are accessible to the useras both tabular and graphical reports. Advantageously, the knowledgedriven composite design optimization system and corresponding processare capable of executing the laminate designer subroutine as a functioncall, which allows the user to determine optimal stacking arrangementsfor selected regions. It should be mentioned that when the internalloads from a finite element solution are available, the laminatedesigner subroutine can calculate the stacking sequence which providesthe greatest margin of safety for the defined geometry and loadconditions.

An alternative preferred embodiment according to the present inventionwill now be described while referring to FIG. 16, which depicts a manualediting method for modifying the critical laminate. As illustrated inFIG. 16, step 850 is first performed to redefine the critical laminateby adjusting the materials, the stacking sequence, the thickness, thefamily, etc., either manually or by the use of an external process. Itshould be mentioned that there are no restrictions on the modificationswhich advantageously can be made, although the desired rules for thenumber of adjacent plies, the extreme limits on the family, the groupingof plies, balance and symmetry of the stack should be followed or theply transition rules will echo the patterns throughout the remaininglocal laminates. Following this step, step 851 is performed to return tothe PACKS process of FIGS. 8A and 8B.

As previously mentioned, the final innovations of the composite designoptimization process are outlined in FIG. 17. In many instances, theuser may wish to add a number of secondary features, e.g., cutouts orstructural reinforcing elements, after designing the overall laminate.The inclusion of these features may locally violate rules previouslyestablished for the laminate connectivity and will affect the global 3-Dply definition. More specifically, the process flowchart illustrates asubroutine by which local features, e.g., holes, are incorporated intothe global laminate after the basic global laminate has been determined.One of ordinary skill in the art will appreciate that this is possiblebecause, while each feature affects the global laminate, each featureaffects the global laminate only locally. Thus, the designeradvantageously can define a set of rules governing the behavior of eachspecific feature, e.g., how the incorporation of a particular featureinto the overall design will affect the global laminate.

The subroutine illustrated in FIG. 17 starts with the performance ofstep 901, in which features, i.e., steps, rabbets, cutouts, joggles,stiffeners, seal grooves, inserts, tabs/lugs, doublers, pads, splices,chamfers, holes and surface extensions, which features will affect theply definition but only locally, are specified. It will be appreciatedthat coming into this stage of the design process, the plies have beendefined in 3-D space while assuming that there are no features.

According to one aspect of the present invention, the featuresadvantageously can be introduced into the design after the base laminatehas been defined. Then, step 902 is performed to determine whether thereare any features to incorporate. When the answer is affirmative, step903 is performed to define the type and geometry of the feature to bedesigned into the laminate structure and then step 904 is performed toapply the knowledge base so as to modify the base laminate according tothe rules specific to that feature. Next, step 905 is executed toredefine the 3-D plies to account for local features. Following step905, a judgment is made at step 906 to determine whether there are anymore features to incorporate. When the answer is affirmative, step 903is repeated; when the answer is negative, step 907 is performed todetermine whether or not to fabricate the panel. It should be mentionedthat when the response at step 902 is negative, step 907 is alsoperformed.

In the event that the decision is YES with respect to fabrication, step908 is performed to define the tooling geometry based upon the inner andthe outer surfaces of the global laminate, step 910 is performed todefine the flattened or as-cut ply shape by feeding the 3-D definitionof every ply to a flattening subroutine, and step 913 is performed tocreate the 3-D ply outline of every ply for a laser projection system inthe lay-up room. It should be mentioned that steps 908, 910 and 913, aswell as the ensuing steps 909, 911, 912 and 914, advantageously can beperformed in parallel, although each of these steps is required priorthe building the structure in step 915. Once step 908 has beencompleted, the tool can be fabricated using the electronic surfacedefinition derived in step 908. Once step 910 is completed, step 911 isperformed to nest the plies, a concept well understood by one ofordinary skill in the art which will not be discussed further. Then,step 912 is performed to cut the individual plies using the electronicdefinition from steps 911 and 912. The cut plies will then be assembledto build the structure in step 915. Moreover, electronic (or paper)drawings preferably are created for use by manufacturing personnelduring step 914. It will be noted that these drawings advantageously canbe used to build the structure during step 915. It will also be notedthat step 916, which permits a return to the composite design overviewof FIG. 7 from the subroutine of FIG. 17, is performed either followingsteps 915 or when the answer to the inquiry of step 907 is negative.

Advantageously, PACKS automates the generation of composite laminatedesigns and illustrations to detail 2-D cross sections of compositelaminate regions, as well as the generation of tables and reports todocument the thickness variations including transitional areas and thenumber of plies within the different regions of the solid. Preferably,the reports provide information on the ply distributions acrossdifferent regions and transitional areas between regions of differentthicknesses (ramps and ramp intersections), while the drawings of the2-D cross sections provide information reflecting detailed capabilities.The preferred composite ply table advantageously can be automaticallydeveloped and maintained throughout each design session. It should benoted that these functionalities preferably are fully parametric andbased upon the outer surface geometry supported in a graphical userinterface.

Beneficially, the graphical user interface enables the user tointeractively identify locations for 2-D section cuts and 3-D slices ofthe ply definition. The user can then interactively select and/or save2-D cross sections and 3-D slices for later recall and redisplay. Thesesections advantageously can be associated with a retrievable planformview. Moreover, the user interface enables the user to manually edit orinput the thickness of the different regions by interactively editing a2-D model. The user interface also supports a sketcher capability forinteractive design and modeling. Thus, the user can alter the designparameters, such as increasing or decreasing the number of plies in aregion or the solid laminate thickness, which triggers the compositedesign optimization system to automatically recompute the surfacegeometry of the plies in addition to the intermediate plies layoutdetails needed for a balanced design and to update all documentation.Thus, in an effort to speed the process of laminate definition, PACKSassists the user in performing three main functions: (1) the design of alaminate; (2) provides laminate visualization at the ply level; and (3)speeds analysis of the laminate. Preferably, PACKS automatically createsa laminate and allows the user to modify the base system rules orparameters through a consistent user interface.

As previously discussed, PACKS provides outputs for several distinctreasons. First, PACKS will provide a printed output, so that hard copiesof the laminate design are available. Thus, the user may select anyview, table or report and print it to either a printer or a file.Second, PACKS advantageously can save data in permanent storage forsubsequent retrieval within PACKS, or other related systems. When theuser elects to save a laminate design in permanent storage, PACKS savesall data necessary to recreate a laminate design during another sessionwith minimal recalculation. For each project, the knowledge drivencomposite design optimization system will be able to track the originallaminate definition, the current laminate definition, and be able todetermine what has changed. Finally, PACKS can output the model invarious formats so that other tools, like manufacturing systems or CADtools advantageously can make use of PACKS output as an input. Forexample, the user may output the drawings and models to a CAD program,e.g., the UNIGRAPHICS (TM) CAD program, preferably by creating anIGES-formatted file for a given view. The user may then read in andmanipulate the drawing in the UNIGRAPHICS (TM) CAD program. It should bementioned that when the view contains tables, the output will beseparated into several files: one main drawing file; and one text filefrom each table. If the user elects to output the entire model to theUNIGRAPHICS (TM) CAD program, PACKS will then save the ply surfaces,outer moldline and inner moldline in an IGES formatted file. Aspreviously mentioned, the user advantageously can output models to theanalytical database for re-analysis.

As discussed in detail above, the knowledge driven composite designoptimization process and corresponding system provide a laminateanalysis overview to the laminate design team. The primary purpose ofthis function is to allow the design team to analyze the quality of alaminate design, allowing the design team to confirm the quality of adesign using, e.g., other company accepted tools. In addition, theknowledge driven composite design optimization process and systemeliminate the need for the design team to manually recreate the inputnecessary to rerun the composite design optimization process system.

The design team advantageously can perform a load analysis on plygeometry created within PACKS. In order to accomplish this task, thecomposite design optimization process will update the analyticaldatabase to reflect any changes in the internal geometry, materials andlaminate definitions. Once updated, the database can be resubmitted foranalysis by another tool. The results of this analysis will bedisplayable, in the same manner as the load analysis of the input FEAmesh.

In addition, the knowledge driven composite design optimization processand corresponding system advantageously can execute the laminatedesigner subroutine as a function call, as described above. Thissubroutine allows the design team to determine optimal stackingarrangements for selected regions. When internal loads from a FEAsolution are available, this subroutine can calculate the stackingsequence which provides the greatest margin of safety for the definedgeometry and load conditions.

Other modifications and variations to the invention will be apparent tothose skilled in the art from the foregoing disclosure and teachings.Thus, while only certain embodiments of the invention have beenspecifically described herein, it will be apparent that numerousmodifications may be made thereto without departing from the spirit andscope of the invention.

What is claimed is:
 1. A knowledge driven composite design optimization process for designing a laminate part comprising steps for:generating a globally optimized 3-D ply definition for a laminate part; and subsequently modifying the 3-D ply definition to include features of the laminate part, wherein said generating and modifying steps are parametrically linked to one another.
 2. The process as recited in claim 1, wherein said generating step further comprises steps for:determining connectivity between a plurality of regions defining the laminate part; subsequently generating ramp features detailing interconnection of the regions defining the laminate part; and displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user.
 3. The process as recited in claim 1, wherein the generating step further comprises the step of optimizing local stacking sequences.
 4. The process as recited in claim 1, wherein:said generating step further comprises generating the globally optimized 3-D ply definition for a laminate part using predetermined rules of laminate design practice; and said modifying step further comprises subsequently modifying the 3-D ply definition to include features which locally violate said predetermined rules of laminate design practice for the laminate part.
 5. A laminate part constructed using a knowledge driven composite design optimization process comprising steps for:generating a globally optimized 3-D ply definition for a laminate part using predetermined optimal rules of laminate design practice; and subsequently modifying the ply definition to include features of the laminate part, wherein said generating and modifying steps are parametrically linked to one another.
 6. The part as recited in claim 5, wherein said generating step further comprises substeps for:determining connectivity between a plurality of regions defining the laminate part; subsequently generating ramp features detailing interconnection of the regions defining the laminate part; displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user; and optimizing local stacking sequences.
 7. The part as recited in claim 5, wherein said modifying step further comprises subsequently modifying the 3-D ply definition to include features which locally modify predetermined optimal rules of laminate design practice for the laminate part.
 8. A knowledge driven composite design optimization process for designing a laminate part comprising:a Parametric Composite Knowledge System (PACKS) module for generating a globally optimized 3-D ply definition for a laminate part in accordance with laminate design transition rules, said PACKS module including:a connectivity subroutine for determining connectivity between a plurality of regions defining the laminate part responsive to said transition rules; a ramp definition subroutine for generating ramp features detailing interconnection of the regions defining the laminate part; and a visualization subroutine for displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user; and a feature module including:a subroutine for modifying the 3-D ply definition to include features which locally modify the global ply solution;wherein said PACKS and said features modules are parametrically linked to one another, and wherein the knowledge driven composite design optimization process applies said PACKS module and said features module in that order as a best practice.
 9. The process as recited in claim 8, wherein said PACKS module further comprises a stacking sequence subroutine for optimizing local stacking sequences.
 10. The process as recited in claim 8, wherein said transition rules determine a number of plies which can be dropped between adjacent ones of said regions and wherein said connectivity subroutine examines all of said plies in a predetermined order to thereby determine which of said plies will be dropped between said regions.
 11. The process as recited in claim 10, wherein said predetermined order is freely selectable from a plurality of predetermined orders.
 12. The process as recited in claim 10, wherein said predetermined order is defined with respect to a centerline ply and a tool surface.
 13. The process as recited in claim 8, wherein:said connectivity subroutine comprises a plurality of connectivity subroutines; said transition rules determine a number of said plies which can be dropped between adjacent ones of said regions; each said connectivity subroutine examines all of said plies with respect to a predetermined order to thereby determine which of said plies will be dropped between said regions, said predetermined order being defined with respect to a centerline ply and a tool surface; and said connectivity subroutine, said ramp definition subroutine and said visualization subroutine are repeated seriatim until all of said connectivity subroutines have been utilized.
 14. A knowledge driven composite design optimization system used in designing a laminate part, comprising:first means for generating a globally optimized 3-D ply definition for the laminate part in accordance with laminate design transition rules, said first means including:second means for determining connectivity between a plurality of regions defining the laminate part responsive to said transition rules; third means for generating ramp features detailing interconnection of the regions defining the laminate part; and fourth means for displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user; and fifth means for modifying the 3-D ply definition to include features which locally modify the global ply solution; wherein said first through fifth means are parametrically linked one to another, and wherein said first through fifth means operate in numerical order as a best practice.
 15. The system as recited in claim 14, wherein said first means further comprises sixth means for optimizing local stacking sequences.
 16. The system as recited in claim 14, wherein said transition rules determine a number of plies which can be dropped between adjacent ones of said regions and wherein said second means examines all of said plies in a predetermined order to thereby determine which of said plies will be dropped between said regions.
 17. The system as recited in claim 16, wherein said predetermined order is freely selectable from a plurality of predetermined orders.
 18. The system as recited in claim 16, wherein said predetermined order is defined with respect to a centerline ply and a tool surface.
 19. The system as recited in claim 14, wherein:said second means is responsive to a plurality of connectivity subroutines; said transition rules determine a number of said plies which can be dropped between adjacent ones of said regions; each said connectivity subroutine examines all of said plies with respect to a predetermined order to thereby determine which of said plies will be dropped between said regions, said predetermined order being defined with respect to a centerline ply and a tool surface; and said second through fourth means are repeatedly operated in numerical order until all of said connectivity subroutines have been utilized.
 20. The system as recited in claim 15, wherein:said second means is responsive to a plurality of connectivity subroutines; said transition rules determine a number of said plies which can be dropped between adjacent ones of said regions; each said connectivity subroutine examines all of said plies with respect to a predetermined order to thereby determine which of said plies will be dropped between said regions, said predetermined order being defined with respect to a centerline ply and a tool surface; and said second through fourth and sixth means are repeatedly operated in that stated order until all of said connectivity subroutines have been utilized.
 21. A computer memory storing computer readable instructions for permitting a computer system to generate a design for a laminate part, said computer readable instructions including a parametric composite knowledge system (PACKS) module for generating a globally optimized 3-D ply definition for a laminate part in accordance with laminate design transition rules, said PACKS module including a connectivity subroutine for determining connectivity between a plurality of regions defining the laminate part responsive to said transition rules, a ramp definition subroutine for generating ramp features detailing interconnection of the regions defining the laminate part, and a visualization subroutine for displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user, and further comprising a feature module including a subroutine for modifying the 3-D ply definition to include features which locally modify the global ply solution, wherein said PACKS and said features modules are parametrically linked to one another, and wherein said PACKS module and said features module are operated in that order.
 22. The computer memory as recited in claim 21, wherein said connectivity subroutine comprises a plurality of connectivity subroutines, wherein said transition rules determine a number of said plies which can be dropped between adjacent ones of said regions, wherein each one of said connectivity subroutines examines all of said plies with respect to a predetermined order to thereby determine which of said plies will be dropped between said regions, said predetermined order being defined with respect to a centerline ply and a tool surface, and wherein said connectivity subroutine, said ramp definition subroutine and said visualization subroutine are repeated seriatim until all of said connectivity subroutines have been utilized. 